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X-Force 3-Inch Varex Cat-Back Exhaust (15-17 GT Fastback)

Item 386428
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      Review & Installation Video

      Justin: Hey guys, I'm Justin with and this is my detailed review of the Varex Catback Exhaust system from X-Force, available for your 2015 and newer Mustang GT. Now you should be checking this thing out if you're after a new catback for your GT and you want to have the ability to change the sound and the loudness of your exhaust from inside the car, and I think that's going to be the biggest appealing factor here with the Varex from X-Force. Now you should also be checking this thing out if you're after a top-quality system in regards to build and material and you don't mind throwing down a little extra money to get all of these things.Now X-Force is a relatively new company here stateside, but they've actually been pretty popular and well-established down in Australia, where the company itself originated. Now the Varex here is the X-Force's bread and butter. It's her patented system. It originated back in 2009 and 2010, but the company as a whole have been gaining a lot of recognition and a lot of popularity here, again, stateside thanks to the system like the Varex and their soon to be released long tube headers. Full disclosure, guys, I actually reviewed the S197 Varex Axelback a little while back and I thought it was something that was going to be a gimmick product. Something that was going to be cool in theory but poor in execution, and honestly I couldn't have been more wrong. The Varex works very well and sounds pretty damn good.Now the truth is, a lot of companies have tried the tunable exhaust thing with varying levels of success, and in my opinion the X-Force is one of the first companies to really nail the design from the execution down to the delivery, but of course ROUSH did a great job as well with their active exhaust systems for the S550.Getting into this system a little bit further here, guys, I think you'll find the centerpiece for this catback are these patented Varex series mufflers here, which do feature this built in butterfly mechanism actually built into the muffler itself. And that's going to operate much like a more modern cutout would. Basically there's a flap in there that opens and closes, and all of it's controlled by the included remote. Unlike those traditional e-cutouts that are generally fully open or fully closed with no options in between, the Varex is going to give you some options here thanks to the adjustment. And as Varex puts it, it's going to give you essentially five mufflers in one. This is achieved by opening that butterfly valve in different increments, changing your sound as you go.So what does this all mean when it comes to your overall sound and volume? Well as you guys heard with the sound clips earlier on here, the difference in sound between these different options is very impressive. Now for starters, with the valve fully closed this thing is very, very quiet. Very similar to what you might find with your factory muffler still in place. Maybe a touch louder, but not by much. However, with everything opened up it's a different story entirely here with the Varex. The sound really does come to life and it's a great sound at that. Nice deep tone overall, no real rasps to speak about here, guys, and a decent amount of volume. So with everything closed up, again, you heard the sound clips, I'm willing to give it a one out of five on my one to wake the neighbor scale here. Very stock sounding setup. But when you do open the Varex completely up, again it does come to life, so that number easily shoots up to a three, maybe even a four out of five again on my wake the neighbors scale.Not going to be the loudest system you'll ever hear, but it does have a nice, deep tone to it and the best part is no interior drone while cruising. Now I can think of several reasons why having full control of the sound and volume of your exhaust would be appealing. The most obvious would be to be quiet when you need it to be. So whether you're entering or leaving the neighborhood or apartment complex, maybe you're driving by Johnny Law, maybe you have your significant other in the car and they're really just not a fan of loud exhaust systems, or maybe even you're just trying to play the role of the sleeper. Whatever the case, the Varex should be able to help you out.Now that you know a little bit more about what to expect when it comes to the sound, let's talk about the build of the Varex here because you are getting more than just that adjustable sound. The Varex, again, is built very, very well. 304 grade stainless steel throughout, which, in my opinion, the best material to use on an exhaust system because it's going to be the best at reducing corrosion. Along with that 304 grade stainless, you are getting 3-inch mandrel bent tubing throughout. Very nice welds on this thing. And finally those four-inch slash cut tips embossed with the X-Force logo. Now the Varex actually does utilize a mid-muffler or mid-resonator system here in this capback, which is going to help round out the tone a little bit along with these Varex performance mufflers, which believe it or not are chambered, and that's where the butterfly valve comes in.Now with that valve fully closed, the Varex is going to act like a chambered muffler through the outside portion of the Varex itself here. However, once that valve is fully opened up, the exhaust flow is going to take the path of least resistance and at that point the Varex is essentially a straight-through flowing muffler, increasing both your sound and performance.Again guys, it's all controlled by the two included key fobs that X-Force throws in. Each one does have two buttons on it. One's going to open the valve and one's going to close it. So this does, again, give you some options here when playing with your sound and experimenting with the key fob. The butterfly valves are powered by a 12-volt power source. X-Force throws in the plug and play harness to get you guys up and running. Now what's going to happen is you're going to plug in both mufflers here using the water-resistant plugs. From that point you fish the harness inside your trunk and then run it to the center console, where it's to be plugged in. This is a total 100% plug and play install.Now before we fully get into the install here with the Varex, let's quickly touch on the price. And as you might expect, things are not exactly cheap at just north of $1300 bucks, but you do have to remember what you're getting here. That fully adjustable sound in addition to the quality 304 grade build here. Again, very solid given the price point. You also have to consider that the ROUSH option, their active exhaust, is only offered in an axelback and it's going to cost you nearly double the price of the Varex here. Just in case you guys were wondering, X-Force does throw a warranty at this thing. One year for the electronics and five years for the mufflers themselves.All right, as for the actual install itself here, guys, well I do have one small nitpick with the Varex and that is the design of the pipe. More specifically, the flanges they use to get everything bolted up. I'd say 99% of the aftermarket S550 catbacks utilize a slip-fit style system for the piping, which just makes everything going on a lot easier as far as the install. Now the Varex, again, they're going to utilize a more traditional flange here. There's nothing really wrong with that, it doesn't fit bad or anything like that, it just makes it a little bit more difficult to install compared to those slip-fit systems. That aside, the rest of this install as far as the exhaust is concerned is pretty standard in the world of catbacks for the S550 GT.A buddy will definitely make this one go a little easier, guys. Trust me. But overall you're just looking at basic hand tools here for the exhaust. Basically a socket set is all you really need. When it comes to the wiring, again guys everything is 100% plug and play here. You're going to want to first plug in the mufflers using the harness. From that portion on there's a little rubber grommet located in the spare tire area in the trunk. You can get the harness through the trunk in there and actually inside the car. From there, you just need to fish it to the center console area, where it will be plugged in to your 12-volt power source or socket. This is probably going to be your most time consuming part because you're going to want to do this right and make sure to hide that wire good so it's a clean install.I'm going to give this one a two out of three wrenches on my overall scale of difficulty. It's not exactly hard, guys, but it is a little bit more involved than a traditional catback install with the S550 GT. We do call this install two hours on the site here, but I wouldn't be surprised if it took you a little longer than that just getting this thing bolted up and, again, running that wire for a clean install.All right guys, to wrap this one up, the Varex from X-Force is a very unique product. It's giving you the ability to change your exhaust tone and volume on the fly, and they've used some really solid materials in the overall build. Now the install might be a little bit more involved and the price might be a little high for some folks on a tight budget, but if having an adjustable exhaust sounds appealing to you, you are not going to be disappointed when checking out the Varex. So be sure to learn more about this catback for your GT right here at

      Product Information

      Features, Description, Reviews, Q&A, Specs & Installation


      • AmericanMuscle Exclusive
      • Varex Cat-Back with "Adjustable Sound"
      • Street Mode, Race Mode and Anywhere in Between
      • Electronically Controlled
      • Mid-Pipe Resonator and Adjustable Chambered Mufflers Included
      • Durable Stainless Steel Construction
      • 3" Mandrel-Bent Tubing
      • 4" Polished Slant Cut Tips
      • Direct Bolt-On, No Cutting or Welding Required
      • (2) Remote Control Key Fobs Included
      • Fits 2015-2017 GT Mustang Fastback Models Only


      Adjustable Sound. By installing a X-Force Varex Cat-Back Exhaust, you can dramatically change the sound of your S550 Mustang's exhaust from a mellow street sound to a rich, throaty race car growl or anywhere between with just a push of a button. The X-Force Varex Cat-Back features electronically adjustable Varex performance mufflers. Close them when driving through a residential area to stay low key. Then open them up to let your coyote howl while cruising down the highway.

      How It Works. Varex performance mufflers utilize a sophisticated internal electronic butterfly valve mechanism to direct the exhaust flow within the muffler. In the open position, the valve "uncorks" the exhaust flow allowing it to take the path of least resistance. The muffler then acts more like a straight-through muffler for a rich throaty race style exhaust note. In the closed position, the valve blocks the exhaust flow, forcing it through the chambered paths to produce a classic, mellow street friendly sound. This unique design is perfect for personalizing the power and sound levels of your Mustang to suit your own specific needs.

      Stainless Steel Construction. This X-Force Varex Cat-Back Exhaust is manufactured from high quality 3" diameter stainless steel tubing for superior durability and corrosion resistance. The System includes a Mid Pipe resonator and features two adjustable chambered mufflers that end with massive 4.0" diameter polished stainless steel tips. The exhaust tips exit in the stock location for impressive muscle car looks and sound.

      Direct Bolt-On Installation. Engineered to be a direct upgrade replacement, this Varex Cat-Back will easily bolt up to the factory piping without any modifications required for a straight forward installation. The control module that powers the butterfly valves can be plugged into your Mustang's 12v accessory outlet for easy plug and play operation or permanently connected to a 12v source - the choice is yours.

      Application. This X-Force Varex Cat-Back Exhaust is designed as a direct fit bolt-on upgrade for the 2015 to 2017 GT Mustang Fastbacks equipped with the DOHC coyote 5.0L V8 engine. This Cat-Back does not fit convertible models.

      Fitment: 2015 2016 2017 Details

      MPN# ES-FM15-VMK-CBS

      CA Residents: WARNING: Cancer and Reproductive Harm -


      Customer Reviews (16)

      Write a Review

      Ratings Summary

      4.3 out of 5 overall rating from 16 customers

      Installation Time: Full Day

      Installation Cost: $100-$250

      • July 22, 2019

        5 2016 GT - Shocker69

        Nice Deep Tone, excellent Craftsmanship. No Drone

        I am extremely happy with this exhaust. Just taking the parts out of the box was like wow. Incredible craftsmanship everything is nice quality, polished to a mirror finish it all looks outstanding. Installing it went very well Took us a couple of hours, two people really helps. Closed it sounds just like stock as far as loudness, open it sounds great. It sounds nice and deep and screams but it’s not super loud. Very reasonable, nothing that will become bothersome. I’ve had it now for two days don’t notice any drone and even cruising with it open, under normal driving conditions it’s still relatively quiet for an aftermarket exhaust. Once you start getting into it half throttle it really starts to wake up. It’s great for getting out of my neighbourhood quietly and coming home late. Very nice product. I am also running long tubes with cat delete.

        Helpful (6)
      • March 29, 2019

        5 2015 GT - zcrom32

        Great quality exhaust with deep tone

        Even though this exhaust has an x-pipe it has a deep tone and not raspy. Materials are really nice. Very shiny/polished finish. My only compliaint is that the keyfob needs to be practically right on top of the remote for it to work. Maybe distance is better if you pay the extra $350 or so for the bluetooth phone add on device. This exhaust used to cost over 2k so is a bargain at the 1300 or so i paid. Also its a complete catback adjustable system that is half the price of the roush axle back only adjustable system.

        Helpful (5)
      • March 06, 2019

        3 2016 GT - AlfonsoS

        Not sure how to feel about them.

        They are for sure quiet. Even when you open them. I’m currently running catted LTH. And I’m sure that’s helping with them not been as quiet as the should be. Reason why I got them was to avoid getting the infamous California exhaust law ticket. Liked the option of controlling the loudness but to be honest they are not even loud at all. I ended up swapping the x force resonator with an X pipe. I defenetly woke up the noise. Now I’m happier with the end result. I wish the would just sell the axle back so you can just pair it with your choice resonator delete....

        Helpful (1)
      • December 13, 2018

        5 2015 GT - bill17 Installation Time: Shop Install Installation Cost: $100-$250

        Great replacement system

        Replaced an x-pile and axle back mufflers. Got the sound I wanted and absolutely no drone at any speed. Only caution is if you want very loud don’t get this system.

        Helpful (4)
      • July 03, 2018

        5 2016 GT - Christopher Installation Time: Shop Install Installation Cost: $250-$500

        Grate sounding exhaust

        Sounds good when fully open and not extremely loud. If you want louder, add an x-pipe to it. Works better with the box controls.

        Helpful (7)
      • June 06, 2018

        3 2017 GT - ToddW Installation Time: Afternoon

        X-Force cat back kit

        I had a competitors brand cat back and it was LOAD-DRONE CITY. Then went with X-Force. Great sound adjustability is great good quality. My only complaint is it is really not load enough. Would like to see an option from X-Force to replace the resonator with just an x-pipe or better yet an H-pipe. Would I buy again? Absolutely! I love it!

        Helpful (4)
      • April 21, 2018

        4 2016 GT - SatinderS Installation Time: Afternoon

        Too quiet

        Look in the finish of this exhaust system is exceptionally excellent. The install to my friend and I about two hours so not so bad. I was a little disappointed with the sound being too low even with the mufflers are open. Instead of spending over thousand dollars on headers with. I bought an x pipe instead with a resonator delete. Made a huge difference. I wish they made this exhaust system without a resonator from factory.

        Helpful (8)
      • September 21, 2017

        5 2015 GT - ThomasJ Installation Time: Shop Install Installation Cost: $100-$250

        Awesome exhaust

        This is a great system you can have the exhaust loud and when you need it quite you can do that too. Plus the Shelby models have a similar system system. Awesome Exhaust!

        Helpful (4)
      • September 17, 2017

        5 2016 GT - Evil550 Installation Time: Afternoon

        Sounds so good

        I bought the 2014 style axleback and custom fit them on to my 16 gt, was a bit of a pain but got it to work paired with my flow master scavenger x pipe and sounds so good in full open very nice tone and good volume without being annoying like the outlaws I previously had on the car. No drone at all. Really loving the fact that I can drive out of the neighborhood at 5 in morning without my girlfriend and neighbors hating me.

        Helpful (9)
      • September 12, 2017

        5 2017 GT - MattH Installation Time: Shop Install Installation Cost: $250-$500


        Super fast shipping, product was packaged great! I have the MBRP long tube headers and the fit was not good at all when trying to do it myself, but I took it to a shop and they did it in a few hours and didn't have any trouble! That was expected though because it's two different exhaust but the final product is amazing! It's super quiet when wanted and a good loud when wanted. The tone is nice and deep and sounds amazing! Highly recommend. I did the wiring myself and it took 30 minutes for a clean install.

        Helpful (4)

      Questions & Answers (14 answers)

      5 Top Rated Questions

      will this exhaust system fit a 2015 GT convertible with the 5/0 motor?

      • The X-Force Varex Cat-Back Exhaust (15-17 GT) will fit both convertible models and coupe models being a direct bolt on.

      Helpful (3)

      How is this different from this one: Besides the price, and it not having "varex" in the title, what is the difference? Both descriptions say they are adjustable electronically.

      • The X-Force Varex Cat-Back features electronically adjustable Varex performance mufflers, the none-Varex system does not have this function.

      Helpful (2)

      My mustang is 2015 and it has x pipe and roush axle back exhaust and JLT Intake with SCT tuning, So if I install the X-FORCE VAREX CAT-BACK EXHAUST do i have to change the tune ?? and if i close the mufflers will it affect the engine because the high flow intake system ??

      • A new tune would not be required. The muffler changes only affect the sound of the system and not engine performance.

      Helpful (1)

      Are these available with black tips

      • At this time the X-Force Varex Cat-Back Exhaust is only offered with polished tips.

      Helpful (1)

      HI I just got the X force app in the phone, but I don't know how to like my exhaust to my phone. if i can use my phone to control my exhaust, that will be so cool! thanks

      • The X-Force Varex Cat-Back Exhaust will come with two key fobs which will be used to adjust the sound of the exhaust.

      Helpful (1)
      Post Your Question
      9 More Questions
      Will this fit a 2016 Mustang GT convertible premium? In the details section it says it will not, but in the comments is says it will. Which one is it? 1 answer
      Are there any X or H-pipes I can buy in conjunction to this exhaust to allow for a louder tone but keep the active exhaust feature? 1 answer
      I’m really hoping there is a way to hardwire the active valves. Is it possible? 1 answer
      Is there a need to relocate oxygen sensors 1 answer
      Hi, Can mufflers be purchased alone like axle back system? 1 answer
      Will this cat back fit a 2011 ragtop? 1 answer
      Hi Why it wont fit the 3.7, V6 ? regards, 1 answer
      Is this a full 3" exhaust, as in no 2.5" stepdowns? 1 answer
      Will this Cat-back connect to any other set of headers? I noticed they use a different clamp style. 1 answer

      Installation & What's in the Box

      Installation Info

      What's in the Box

      • (1) Passenger Side Muffler Assembly
      • (1) Driver Side Muffler Assembly
      • (1) Resonator Mid-Pipe
      • (2) Exhaust Hangers
      • (1) Control Module
      • (2) Key FOB's
      • Wiring Harness

      Tech Specs

      Cat-Back Exhaust Specifications
      Piping Material:Stainless Steel Tip Material :Polished Stainless Steel
      Piping Size:3"Tip Size:4"
      Muffler Type:ChamberedFitment:2015-2017 GT Fastback

      Will It Fit My Mustang

      • GT - 15, 16, 17

      Fits fastbacks only, does not fit convertible models.

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