Catback Exhaust System - Un-Resonated - 11-21 WRX/STI Sedan

( 3 Reviews )
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With so many catback options available, our goal was to create a unique, refined sound in an extremely high quality system. We've been casually referring to it as the gentleman's catback around the shop, to ensure that our mission wasn't lost in all of the craziness. We also wanted to produce a single system that would fit as many models as possible. Using a unique hanger design and by including a set of four custom polyurethane hangers with each kit, we've been able to fit all EJ and FA20DIT WRX and STI sedans from 2011 to 2021.

Why GrimmSpeed?

Sometimes, this explanation is long and technical, especially where performance is concerned. This time, it's simple. The GrimmSpeed engineering and manufacturing teams are known for designing and producing products that use high quality materials, offer perfect fitment and superior craftsmanship and are durable. These catbacks are no different. If you're tired of your catback rattling against heat shields, tips hanging too low, crooked or uneven, exhaust that's too loud or materials that are rusting or failing, then we have the solution for you. Beyond the product (and it's Lifetime Warranty!), the GrimmSpeed customer service team is ready to help you with any questions or concerns you might have.

We stand behind our products 100% and our goal is to offer you a customer experience that makes you want to stand behind them as well.

Quick Specs

  • Custom dual outlet mufflers - dual perforated tubes offer quieter, more refined tone
  • Quad 3.5" double-wall, angle-cut tips - our most commonly requested configuration
  • Resonated or Un-resonated options - the choice is yours, although we recommend resonated for the FA20DIT and un-resonated for the EJ
  • 304 Stainless Steel construction - genuine American 304SS material to withstand the elements and abuse
  • 1/2in thick flanges - all 7 flanges are laser cut from the same 1/2in thick stainless plate for perfect sealing, easy installation and extreme durability
  • Flex section - your motor and mufflers are both mounted using rubber or poly mounts and can move independent of one another - if there isn't a flex section or donut gasket allowing relative movement, there's a much greater likelihood of damage to your exhaust or turbo
  • Custom polyurethane hangers - these hangers keep your exhaust where it needs to be, freeing you from rattles, melted bumpers and so on
  • TIG welded - each catback is hand TIG welded just across the hall from the engineering offices that they were designed in, ensuring craftsmanship that does our Lifetime Warranty justice
  • GrimmSpeed Lifetime Warranty - buy knowing that we stand behind our products and customers 100%


  • 2011-21 Subaru WRX Sedan
  • 2011-21 Subaru STI Sedan

Included Components

  • 2x Muffler Section
  • 1x Y-Pipe
  • 1x Un-resonated Midpipe
  • 4x Two-position Poly Exhaust Hangers
  • ALL Gaskets and Hardware
  • 2x GrimmSpeed License Plate Frame
  • 1x GrimmSpeed Decal

Sound Clips

3 Reviews

Garret Wiley 28th Sep 2021

Perfect sound on a 21 STI Limited

The quality of this kit is amazing. Fit is precise. Welds even more precise. I’m glad I went with the recommendation of no resonator. I am continually impressed with the quality of the products grimmspeed makes. The sound is deep but not obnoxious. It’s perfect. This car has a stock tune so I had the adapter for factory down pipe included. I was worried that this would somehow disappoint me because I wasn’t quite ready to make the jump and buy a down pipe and boost controller and get a stage 3 tune. But when I turned it over and heard the deep tone coming out of the exhaust it was the most satisfying experience I’ve had since buying the car. Sound clips don’t do it justice. It’s loud enough that you hear it at idle . But at cruising speeds it’s tame and doesn’t have that annoying drone. Where it shines is when you start driving it hard in Sport plus . It sound great just driving normally, but when you open the throttle, their won’t be any doubt from cars around you where that sound is coming from. I was slightly concerned about putting this on a 2021 STI but the fit seems perfect. I am glad I went with this cat back. Their are a lot of choices on the market but I’ll stick with the quality and craftsmanship that made my boxer come to life. Also shout out to Marissa. Customer service is amazing. I’ve called and emailed multiple times over mundane things and every time I have an interaction with customer service it’s always positive. I highly recommend this exhaust to anyone with a EJ25. I fell in love with this company after seeing one of their TMIC intercoolers. I’ve replaced almost everything I can without a tune. For those who want the sound to mirror the performance. This is the exhaust for you.

Yolanda 14th Oct 2019


This catback is amazing, I shopped around for weeks trying to find the best one. Many mentioned GrimmSpeed, I must say it lived up to all the hype. Easy install, and saw improvement instantly with my car. Only thing was left muffler had a minor dent upon arrival, but hey product is still amazing and I’m very happy with my purchase.

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