Choosing the best cat-back exhaust system for your Subaru STI involves balancing sound, performance gains, build quality, and price. The Invidia Q300 stands out as the overall top pick thanks to its balanced tone and improved airflow, but models like the BORLA offer a more aggressive sound for enthusiasts willing to invest more. Meanwhile, options like the PHILTOP provide budget-friendly solutions that still boost performance, though they may lack the premium finish of higher-end systems. The main tradeoffs in this category typically revolve around sound level versus daily drivability and the cost of premium materials versus affordability. Continue reading for a detailed breakdown of each system and how they align with your specific goals.
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Key Takeaways
- Top picks like the Invidia Q300 deliver a balanced blend of sound and performance, making them versatile for most drivers.
- Premium systems such as Tomei‘s Titanium Kit prioritize lightweight construction and durability, suitable for serious enthusiasts.
- Budget-friendly options like PHILTOP can boost performance but often sacrifice some build quality and sound refinement.
- Material choice, especially titanium versus stainless steel, significantly impacts durability and weight but also price.
- Sound profile varies widely; consider whether you want a subtle upgrade or an aggressive exhaust note for daily driving or show.
| KAX Cat Back Exhaust System Compatible with 2015-2017 Subaru WRX/WRX STI |  | Best Budget-Friendly Upgrade | Fitment: 2015-2017 Subaru WRX/WRX STI | Material: Stainless steel | Weight: 25.1 pounds | VIEW LATEST PRICE | See Our Full Breakdown |
| Invidia HS15STIGM4ST Exhaust System for 2015+ Subaru WRX/STi Gemini/R400 with Quad Titanium Tip |  | Best for Performance Gains | Brand: Invidia | Model Number: HS15STIGM4ST | Item Weight: 49.5 pounds | VIEW LATEST PRICE | See Our Full Breakdown |
| PHILTOP Cat-Back Exhaust System for 2015-2017 Subaru WRX/WRX STI |  | Best for Easy Installation and Reliability | Vehicle Fitment: 2015-2017 Subaru WRX/WRX STI | Material: T-304 stainless steel | Installation: Direct bolt-on, no drilling or modifications needed | VIEW LATEST PRICE | See Our Full Breakdown |
| Replacement Exhaust System for 2015-2021 Subaru WRX STI – Stainless Steel Double Wall Quad Tips, Cat Back |  | Best for Long-Term Durability and Appearance | Fits: 2015-2021 Subaru WRX STI | Material: Stainless Steel | Tips: Double Wall Quad Tips | VIEW LATEST PRICE | See Our Full Breakdown |
| DNA MOTORING CBE-WRX15-D Stainless Steel Cat Back Exhaust System for 2015-2017 Subaru WRX & STI Sedan |  | Best for Sound Tuning and Power | Fitment: 2015-2017 Subaru WRX & STI Sedan | Material: T-304 Stainless Steel | Muffler Tip Diameter: 4 inches | VIEW LATEST PRICE | See Our Full Breakdown |
| BORLA 140595 Cat-Back Performance Exhaust System for 2015-2021 Subaru Impreza WRX & WRX STI 2.0L/2.5L |  | Best Overall | Material: T-304 Stainless Steel | Installation: Bolt On | Construction: All Welded | VIEW LATEST PRICE | See Our Full Breakdown |
| Invidia N1 Twin Outlet Single Layer Cat-Back Exhaust System with Titanium Tip for Subaru WRX STI 4-Door |  | Best for Performance Gains | Application: Subaru WRX STI 2008-Up | Piping diameter: 76 millimeter | Tip size: 101 millimeter | VIEW LATEST PRICE | See Our Full Breakdown |
| Invidia Q300 Rolled Titanium Quad Tip Cat-Back Exhaust System for Subaru WRX/STI |  | Best Deep Sound | Fitment: 2015-Up Subaru WRX/STI 4 Door | Pipe size: 76mm (3 inches) | Tip size: 110mm (4.3 inches) | VIEW LATEST PRICE | See Our Full Breakdown |
| Tomei Full Titanium Muffler Kit for 2008-2021 Subaru WRX and STI Sedan – Single Exit |  | Best Lightweight Performance | Compatibility: 2008-2014 WRX EJ sedan, 2011-2021 STI EJ sedan, 2015-2021 WRX FA20DIT sedan | Weight: 16 lbs | Material: Titanium | VIEW LATEST PRICE | See Our Full Breakdown |
| cat-back exhaust systems for Subaru STI | Material |
|---|---|
| KAX Cat Back Exhaust System Co | Stainless steel |
| Invidia HS15STIGM4ST Exhaust S | Titanium |
| PHILTOP Cat-Back Exhaust Syste | T-304 stainless steel |
| Replacement Exhaust System for | Stainless Steel |
| DNA MOTORING CBE-WRX15-D Stain | T-304 Stainless Steel |
| BORLA 140595 Cat-Back Performa | T-304 Stainless Steel |
| Invidia N1 Twin Outlet Single | SUS304 stainless steel |
| Invidia Q300 Rolled Titanium Q | SUS304 stainless steel |
| Tomei Full Titanium Muffler Ki | Titanium |
More Details on Our Top Picks
KAX Cat Back Exhaust System Compatible with 2015-2017 Subaru WRX/WRX STI
The KAX Cat Back Exhaust System stands out for providing a durable, corrosion-resistant option that simplifies installation without cutting or drilling. Compared to aftermarket options like the Invidia HS15STIGM4ST, it offers a more straightforward bolt-on process, but its heavier weight—over 25 pounds—may slightly impact handling. Customers appreciate its ability to improve exhaust flow and sound, though some report mixed performance results. This pick makes the most sense for owners seeking a reliable, cost-effective upgrade who prioritize ease of installation over ultimate performance gains.
Pros:- Durable and corrosion-resistant stainless steel construction
- Easy installation without cutting or drilling
- Improves exhaust flow and reduces noise
Cons:- Customer reviews indicate mixed satisfaction with performance
- Heavy weight may affect vehicle handling
Best for: Budget-conscious owners looking for a straightforward, durable upgrade that improves sound and exhaust flow without complicated modifications
Not ideal for: Performance enthusiasts seeking maximum horsepower or lightweight components, as this system’s weight and limited power gains may fall short of expectations
- Fitment:2015-2017 Subaru WRX/WRX STI
- Material:Stainless steel
- Weight:25.1 pounds
- Dimensions:45.67 x 9.06 x 17.32 inches
- Manufacturer Part Number:4791ESK062SUS
Our verdict“This system is ideal for budget-minded owners who want a simple, durable upgrade that enhances sound and exhaust flow without high costs.”
Invidia HS15STIGM4ST Exhaust System for 2015+ Subaru WRX/STi Gemini/R400 with Quad Titanium Tip
The Invidia HS15STIGM4ST excels in boosting horsepower with its high-quality titanium construction and aggressive quad tips, making it well-suited for those who want a noticeable performance increase. Unlike the slightly simpler PHILTOP setup, this system’s titanium tips add a sporty aesthetic, but its hefty weight—nearing 50 pounds—may require professional installation or modification. It’s a clear choice for drivers aiming for maximum power and a refined sound, though at a premium price and with potential installation challenges.
Pros:- Provides a noticeable increase in horsepower
- High-quality titanium tips add a sporty appearance
- Easy bolt-on installation compatible with stock or Invidia exhausts
Cons:- Heavy weight at 49.5 pounds may be cumbersome
- Installation may require professional help
Best for: Performance-focused owners who want a significant horsepower boost and a sporty, high-end look
Not ideal for: Casual drivers or those prioritizing affordability, as the weight and cost may be prohibitive
- Brand:Invidia
- Model Number:HS15STIGM4ST
- Item Weight:49.5 pounds
- Included Components:Automotive Exhaust Gaskets
- Application:2015+ Subaru WRX/STi Gemini/R400
- Material:Titanium
Our verdict“This system is best suited for enthusiasts seeking maximum power and a premium aesthetic, accepting the added weight and cost.”
PHILTOP Cat-Back Exhaust System for 2015-2017 Subaru WRX/WRX STI
The PHILTOP Cat-Back Exhaust System offers a straightforward bolt-on fit with no modifications required, making it ideal for owners who want dependable performance with minimal fuss. Unlike the Invidia system, it’s made from high-quality T-304 stainless steel, ensuring durability, but it may produce a louder sound that could be undesirable for some. Installation is simple for those with basic mechanical skills, but it might not satisfy those seeking aggressive sound or maximum power gains.
Pros:- Improves exhaust sound and performance
- Made of high-quality stainless steel for durability
- Easy to install without modifications
Cons:- May be louder than stock, which some may find excessive
- Installation might require basic mechanical skills
Best for: Owners who prioritize ease of installation and durability, especially those less comfortable with complex modifications
Not ideal for: Performance enthusiasts wanting aggressive sound or significant power improvements, as it emphasizes simplicity over performance tuning
- Vehicle Fitment:2015-2017 Subaru WRX/WRX STI
- Material:T-304 stainless steel
- Installation:Direct bolt-on, no drilling or modifications needed
- Includes:Gaskets and hardware
Our verdict“This system suits owners seeking a reliable, easy-to-install upgrade that enhances sound and durability without complex modifications.”
Replacement Exhaust System for 2015-2021 Subaru WRX STI – Stainless Steel Double Wall Quad Tips, Cat Back
This Replacement Exhaust System is designed for a wide model range, offering a stainless steel build with double wall quad tips that elevate the vehicle’s aesthetic. Unlike the simpler PHILTOP or KAX options, it includes a mid-pipe kit and hardware, making it a comprehensive upgrade. However, its weight—around 45 pounds—may require sturdy support, and it doesn’t fit aftermarket mods like the SPT mid pipe. It’s a solid choice for owners wanting a durable, high-quality system with a polished look, but limited warranty and compatibility could be concerns.
Pros:- Durable stainless steel construction
- Enhanced appearance with polished finish
- Includes complete hardware and mid-pipe kit
Cons:- Heavy weight may require sturdy support
- Limited warranty period of one year
Best for: Owners seeking a durable, visually appealing exhaust upgrade with complete hardware for long-term reliability
Not ideal for: Owners with aftermarket mid pipes or those seeking lightweight setups, due to its weight and limited compatibility
- Fits:2015-2021 Subaru WRX STI
- Material:Stainless Steel
- Tips:Double Wall Quad Tips
- Type:Cat Back Exhaust System
- Package Includes:Quad Tips, Mid-Pipe Kit, Hardware
Our verdict“This system is best for owners who want a durable, visually striking upgrade with comprehensive hardware for long-term use.”
DNA MOTORING CBE-WRX15-D Stainless Steel Cat Back Exhaust System for 2015-2017 Subaru WRX & STI Sedan
The DNA MOTORING CBE-WRX15-D is engineered for owners who want an aggressive sound and noticeable torque improvements. Made from high-quality T-304 stainless steel with mandrel bends, it effectively increases horsepower and provides a deeper exhaust tone. Compared to the Invidia system, it offers a more tuned exhaust note, but its louder sound could be overwhelming for daily driving. Installation is straightforward but may require mechanical skill or professional help, especially if aiming for a perfect fit.
Pros:- Made of durable T-304 stainless steel with mandrel bends
- Increases horsepower and torque effectively
- Provides an aggressive, deep exhaust tone
Cons:- May produce louder sound that some find excessive
- Installation may require mechanical skill
Best for: Owners wanting a louder, more aggressive exhaust tone with improved torque and horsepower
Not ideal for: Those who prefer a stealthy or quieter ride, as this system may produce excessive noise and require mechanical expertise for installation
- Fitment:2015-2017 Subaru WRX & STI Sedan
- Material:T-304 Stainless Steel
- Muffler Tip Diameter:4 inches
- Inlet Diameter:2.5 inches
- Main Piping Diameter:2.5 inches
- Warranty:Contact seller for details
Our verdict“This system is best suited for owners seeking a loud, performance-oriented upgrade that enhances torque and sound but may be too aggressive for some daily drivers.”
BORLA 140595 Cat-Back Performance Exhaust System for 2015-2021 Subaru Impreza WRX & WRX STI 2.0L/2.5L
This BORLA system stands out for its durable T-304 stainless steel construction and distinctive sound, making it a top choice for enthusiasts who want a combination of performance and durability. Compared to the Invidia Q300, BORLA offers a more refined tone, though it is heavier at 48 lbs, which could be a concern for weight-sensitive builds. Its all-welded design and USA manufacturing add to its reliability, but the weight might impact handling slightly. This pick makes the most sense for drivers seeking a long-lasting exhaust with a deep, aggressive sound without sacrificing quality.
Pros:- Durable T-304 stainless steel construction
- Powerful, aggressive exhaust sound
- Easy bolt-on installation
- Made in the USA with a lifetime warranty
Cons:- Heavy weight at 48 lbs, which may slightly affect handling
- May produce more noise than stock, potentially bothering neighbors or noise-sensitive drivers
Best for: Subaru STI owners who prioritize durability, all-American manufacturing, and a powerful exhaust tone.
Not ideal for: Performance-focused drivers seeking the lightest possible system or those on a strict weight budget, as this system is relatively heavy.
- Material:T-304 Stainless Steel
- Installation:Bolt On
- Construction:All Welded
- Dimensions:45 x 31 x 11 inches
- Weight:48 lbs
- Made in:USA
- Warranty:Manufacturer’s Warranty
Our verdict“This system is ideal for enthusiasts wanting a durable, USA-made exhaust with a commanding sound and reliable build quality.”
Invidia N1 Twin Outlet Single Layer Cat-Back Exhaust System with Titanium Tip for Subaru WRX STI 4-Door
The Invidia N1 excels at boosting horsepower and torque thanks to its mandrel-bent piping and CNC-machined flanges, making it a favorite for those who want noticeable performance improvements. Unlike the BORLA, which emphasizes durability and sound, the N1 focuses on flow efficiency, delivering more power. The polished titanium tip adds aesthetic flair, but the system can be quite loud, which might not suit daily drivers or noise-sensitive owners. Its higher price reflects the quality materials and performance gains, making it a smart choice for those seeking serious power upgrades.
Pros:- Significant horsepower and torque improvements
- High-quality SUS304 stainless steel and CNC-machined flanges
- Mandrel-bent piping for optimal exhaust flow
- Aesthetic polished titanium tip
Cons:- Potentially very loud, which could be intrusive
- Installation may require technical skills or professional help
- Premium price point
Best for: Performance-oriented Subaru STI owners who want maximum horsepower and torque increases and don’t mind higher noise levels.
Not ideal for: Daily drivers or commuters who prefer a quieter exhaust or are sensitive to noise, as this system can be loud during operation.
- Application:Subaru WRX STI 2008-Up
- Piping diameter:76 millimeter
- Tip size:101 millimeter
- Material:SUS304 stainless steel
- Finish:Polished
- Manufactured:CNC-machined flanges
Our verdict“This system is best suited for drivers seeking maximum performance gains and a bold exhaust note, accepting the increase in noise and cost.”
Invidia Q300 Rolled Titanium Quad Tip Cat-Back Exhaust System for Subaru WRX/STI
The Invidia Q300 offers a deep, sporty exhaust tone thanks to its flat bottom muffler and rolled titanium quad tips, making it a compelling choice for those who want a rich sound without sacrificing quality. It improves horsepower and torque similarly to the Invidia N1 but with a slightly more subdued tone, ideal for drivers who want performance but less volume. Its TIG-welded SUS304 stainless steel ensures durability, yet installation might require professional help, especially for those unfamiliar with exhaust modifications. The aesthetic appeal of the titanium tips adds to its visual appeal, making it suitable for enthusiasts looking for style and sound.
Pros:- Deep, sporty exhaust sound
- High-quality SUS304 stainless steel construction
- CNC-machined flanges and TIG welding for durability
- Rolled titanium quad tips for aesthetic appeal
Cons:- Installation may require professional help
- Potentially loud for some users
- Higher price compared to simpler systems
Best for: Subaru owners who want a sporty sound with aesthetic appeal and reliable build quality, without excessive noise.
Not ideal for: Owners seeking the loudest possible exhaust or those who prefer a simpler, single-tip design, as this system emphasizes style and sound depth.
- Fitment:2015-Up Subaru WRX/STI 4 Door
- Pipe size:76mm (3 inches)
- Tip size:110mm (4.3 inches)
- Material:SUS304 stainless steel
- Construction:CNC-machined flanges, TIG welding
- Design:Flat bottom muffler, rolled titanium quad tips
Our verdict“Ideal for drivers who want a deep, sporty exhaust tone with high-quality craftsmanship and stylish titanium tips, accepting installation complexity and higher cost.”
Tomei Full Titanium Muffler Kit for 2008-2021 Subaru WRX and STI Sedan – Single Exit
The Tomei Titanium Muffler Kit is unmatched when it comes to weight savings, shedding over 35 pounds compared to factory systems, which translates into better handling and acceleration. Its high-grade titanium construction also promises excellent durability and heat resistance, making it a favorite among track enthusiasts and weight-conscious owners. Unlike the steel-based options like the Invidia systems, Tomei’s lightweight design is more expensive and may require specialized tools or skills for installation. This kit is perfect for those who want a significant reduction in weight without sacrificing durability, but it’s best suited for experienced tuners or those with access to professional installation services.
Pros:- Over 35 pounds weight reduction over stock exhaust
- High durability and heat resistance of titanium
- Lightweight at approximately 16 lbs
- Excellent for weight reduction and performance
Cons:- Higher cost due to titanium construction
- Installation may require specialized tools or skills
- Limited to single exit design
Best for: Subaru owners seeking the lightest possible exhaust system to enhance handling and acceleration, especially for track use or weight reduction projects.
Not ideal for: Casual drivers or those on a tight budget, as titanium systems tend to be more expensive and require specialized installation skills.
- Compatibility:2008-2014 WRX EJ sedan, 2011-2021 STI EJ sedan, 2015-2021 WRX FA20DIT sedan
- Weight:16 lbs
- Material:Titanium
- Exit Type:Single Exit
Our verdict“This kit is perfect for weight-conscious drivers and enthusiasts aiming for maximum reduction without compromising durability, provided they can handle the installation complexity and cost.”
How We Picked
Products were evaluated based on a combination of performance improvements, build quality, sound customization, ease of installation, and overall value. We prioritized systems that offered noticeable gains in horsepower and torque while maintaining durability under the stress of daily use. Ease of installation was another key factor, especially for DIY enthusiasts, along with the quality of materials used to ensure longevity. The ranking reflects a balance between cost and features, with higher-end options earning their place through premium craftsmanship and performance benefits. Systems that excelled across multiple categories were rated higher, ensuring the list offers options for different priorities and budgets.| cat-back exhaust systems for Subaru STI | Material |
|---|---|
| KAX Cat Back Exhaust System Co | Stainless steel |
| Invidia HS15STIGM4ST Exhaust S | Titanium |
| PHILTOP Cat-Back Exhaust Syste | T-304 stainless steel |
| Replacement Exhaust System for | Stainless Steel |
| DNA MOTORING CBE-WRX15-D Stain | T-304 Stainless Steel |
| BORLA 140595 Cat-Back Performa | T-304 Stainless Steel |
| Invidia N1 Twin Outlet Single | SUS304 stainless steel |
| Invidia Q300 Rolled Titanium Q | SUS304 stainless steel |
| Tomei Full Titanium Muffler Ki | Titanium |
Factors to Consider When Choosing Best Cat-back Exhaust Systems For Subaru STI
When selecting a cat-back exhaust system for your Subaru STI, it’s essential to consider factors beyond just style and price. Performance gains, sound level, material durability, and ease of installation all play crucial roles in finding the best fit for your needs. Understanding these factors helps prevent common mistakes, such as choosing a system that’s too loud for daily driving or one that doesn’t match your performance expectations. This guide will walk you through the key considerations to make an informed decision and avoid costly missteps.Performance and Power Gains
Look for systems designed to improve airflow and reduce backpressure, which can translate into measurable horsepower and torque gains. Not all exhausts deliver the same level of performance improvement, so check for reputable brands with proven results. Keep in mind that significant gains often come with increased noise, so balance your desire for power with your comfort level in daily driving.
Sound and Noise Level
The sound profile of an exhaust greatly influences your driving experience. Some systems, like the Invidia N1 or Q300, deliver a deep, aggressive tone, ideal for spirited driving. Others, such as budget options, may be quieter or produce a drone that’s distracting on long trips. Consider whether you prefer a subtle enhancement or a loud, attention-grabbing exhaust, and choose accordingly.
Material and Durability
Stainless steel remains the most common material, offering good corrosion resistance and strength at a reasonable price. Titanium, used in premium systems like Tomei, provides even lighter weight and superior durability, especially in harsh conditions, but at a higher cost. Investing in quality materials extends the lifespan of your exhaust, making it a better value over time.
Installation and Compatibility
Ease of installation varies between systems; some are bolt-on and straightforward, while others may require welding or custom fitting. Always verify compatibility with your specific Subaru STI model year to avoid fitment issues. If you lack mechanical skills, consider systems that come with detailed instructions or professional installation options to prevent damage and ensure optimal performance.
Price and Value
While high-end systems often deliver superior performance and sound quality, they come with a higher price tag. Budget options can still enhance your car’s feel and sound, but may not last as long or look as refined. Determine your priorities—whether it’s maximum performance, a specific sound, or budget constraints—to find the best value that matches your expectations.
Frequently Asked Questions
Will installing a cat-back exhaust system void my Subaru STI warranty?
Installing an aftermarket exhaust system can potentially impact your warranty, especially if it causes engine issues or damages other components. However, many reputable brands design their systems to be bolt-on upgrades that won’t void the entire warranty. It’s advisable to check with your dealer or review your warranty policy before installation to understand any limitations or conditions.
Is a titanium exhaust worth the extra cost for my Subaru STI?
Titanium exhausts are significantly lighter and more resistant to corrosion than stainless steel, which can benefit performance and longevity, especially in harsh climates. For dedicated enthusiasts or those seeking the best weight savings and durability, investing in titanium makes sense. However, for casual drivers, stainless steel systems often provide excellent value at a lower price point, making titanium more of a premium choice.
How loud should my exhaust be if I plan to daily drive my STI?
The ideal noise level depends on your personal preference and local noise regulations. Many aftermarket systems can be tuned or chosen for a quieter, more refined tone suitable for daily use, while others are intentionally loud for aggressive driving. Consider your tolerance for noise and whether a louder exhaust might attract unwanted attention or cause complaints from neighbors.
Can I install an aftermarket exhaust myself, or should I hire a professional?
Many cat-back exhaust systems are designed for bolt-on installation, making them accessible for experienced DIYers with basic tools. However, some systems may require welding or more advanced skills, especially if modifications are needed for perfect fitment. If you’re unsure about your mechanical skills or want to ensure a perfect fit, professional installation is a wise investment to avoid potential damage and guarantee optimal performance.
How do I choose between stainless steel and titanium exhaust systems?
Stainless steel offers good durability and cost savings, making it a popular choice for most drivers. Titanium, on the other hand, provides superior lightness and corrosion resistance, which benefits performance-focused builds and those living in coastal or harsh environments. Your budget and performance goals should guide your choice, with titanium being a premium investment for enthusiasts seeking the best in weight savings and longevity.
Conclusion
For most daily drivers seeking a balanced upgrade, the Invidia Q300 offers excellent sound and performance without breaking the bank. Enthusiasts prioritizing weight savings and durability will find the Tomei Titanium Kit to be a worthwhile investment. Budget-conscious buyers can consider the PHILTOP for a cost-effective boost, while those after a premium, aggressive tone might prefer the BORLA or Invidia N1. Ultimately, your choice should align with your driving style, budget, and performance goals—there’s an ideal system for every Subaru STI owner in this lineup.
