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XForce Varex Cat-Back Exhaust (15-20 EcoBoost Fastback w/o Active Exhaust)

Item 390327
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      Video Review & Installation

      You should be checking out the Varex from XForce if you're shopping for a cat-back for your S550 EcoBoost and you want the ability to change the sound and loudness of your exhaust on the fly from inside of the car, and that's gonna be the biggest differentiator with the Varex. Not only that, but the Varex will also appeal to those owners out there who would like a top-quality system when it comes to materials and someone that doesn't mind spending a little bit to get all of this. The install for this is easy. It's a one out of three wrenches on the difficulty meter since cat-backs for the S550 simply bolt right up, but I'll get more into that later. You might not have heard of XForce before, but they've actually been a very popular and established brand down in Australia for some time now where they originated. The Varex is their patented system, and it's been around for a few years, so I wouldn't say that this system is new to the game. This is a tunable exhaust, and I'll say that a lot of companies have tried tunable exhaust things before with varying levels of success. XForce and Roush are the two companies that I think did a good job with this design. You have options with the exhaust, too. You aren't stuck with either just open or closed, and I'll explain more in a second. Getting into it a little bit further, like usual with a cat-back, the main player of this cat-back in the centerpiece is the patented Varex mufflers that feature a mechanism, or a butterfly, within the actual muffler itself that functions a lot like a traditional cutout would, and all this is controlled by the included remotes. Now, unlike those traditional cutouts that are generally fully open or fully shut with no options in between, the Varex gives you an option to customize your sound with a level of adjustment, essentially giving you five different mufflers in one, as Varex puts it. This is achieved by opening the butterfly in different increments, which will change the tone along the way. So, what does this all mean when it comes to sound and overall volume? Now, you guys heard the sound clips, and I'll say it again, the difference in sound is noticeable. With the valve fully closed, the sound and volume is very similar to what you find with a factory muffler still in place, maybe just a touch louder, but not by much. With the valve fully open, it's another story. The sound really comes to life, and it's a good sound at that. There's plenty of tone, no rasp to really speak of, and a decent amount of overall volume. With everything closed up, I'd give this system a one out of five on the one to five scale. With everything opened up, that number easily shoots up to a strong two out of five on the loudness scale. It's not the loudest setup, but it does have a nice deep tone with zero drone inside the car while cruising. There's a number of reasons why having full control over your tone and volume might be appealing. The most obvious would be to have the ability or the option to be quiet when you want to be or when you need to be, like entering or leaving a neighborhood, or an apartment complex, or driving by Johnny Law, or maybe you have your significant other in the car, and they're not a fan of loud exhaust, or maybe you're trying to play the role of a sleeper. Whatever the case, the Varex will be able to help you out. Now that you know what to expect, let's talk about the build of the Varex, because, again, you're getting more than just the adjustable sound here. For starters, you're getting a full 304 grade stainless steel throughout, the best material, in my opinion, when it comes to exhaust, and especially when it comes to resisting corrosion. The Varex does bolt right up to the factory downpipe then steps up to a full 3-inch mandrel-bent tubing throughout. It's a very nice weld, and 4-inch brightly polished, slash-cut tips. XForce also incorporates a midpipe resonator in the system to help round out the tone a little bit in conjunction with the Varex performance mufflers, which are chambered, and that's where the butterfly valve comes in. With the valve fully closed, the exhaust flow goes through more of a chambered section of the muffler, keeping things relatively mild. However, once opened, the exhaust takes the path of least resistance and essentially acts as a straight-through muffler, increasing both sound and performance. It's all operated by the key fob that XForce gives you. XForce gives you two of these, and each fob has two buttons on it, one to open the valve and one to close it. And, again, you can play around with the sound by experimenting with the fob and the buttons. The butterflies are powered by a 12-volt source. XForce includes the plug-and-play harness to get you up and running. The harness will plug into both mufflers using water-resistant plugs, and from there it's fished inside the car through the trunk to be plugged in the 12-volt power socket inside of the center console. It's a total plug-and-play deal here, guys. When it comes to price, as you probably expected, this isn't what I consider a cheap system. You can expect to pay just south of the $1,000 mark, but you have to keep in mind what you're getting here. You get the adjustable tone and the full 304 grade stainless, and that's pretty solid for the price, especially when you consider the Roush version, which is only offered in an axle-back, by the way, and it's double the price of the Varex. And in case you were wondering, XForce does back the Varex with a one-year warranty on the electronics and the butterfly and a five-year warranty on the mufflers themselves. When it comes to the install, you can expect to spend about two hours on it. It's gonna be a one out of three wrenches on the difficulty meter, pretty much looking at the normal cat-back install with a few exceptions. Unlike most other aftermarket cat-backs for the S550 that utilize the slip fit style piping to get everything together, the Varex uses a traditional flange, joining the resonator portion of the cat-back, which isn't a huge deal. It just makes the install slightly more difficult compared to the slip fit designs. That aside, the rest of the install is pretty standard in the world of cat-backs. Having a friend help you with this will certainly make your life easier, but, overall, just basic hand tools, including a socket set for the exhaust portion. When it comes to the wiring, again, everything is completely plug-and-play. With the harness connected to the mufflers, run it up into the trunk through the removable grommet in the spare tire area, and then from there you need to get it to the center console area to be plugged into the 12-volt socket. This might take you a little time to do this right as you're probably gonna wanna hide the wire under the carpet for a clean install. Wrapping things up here with the XForce Varex cat-back exhaust, this is a system that'll fit the 2015 and newer EcoBoost Mustang. I suggest you check it out more online for yourself. For all things Mustang, keep it 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
      • Not Compatible with Active Exhaust
      • Fits 2015-2020 EcoBoost Fastback Mustangs


      Adjustable Exhaust Sound. An XForce Varex Cat-Back will allow you to change the sound of your EcoBoost Mustang's exhaust from a smooth street sound to a rich, throaty race car growl or anywhere in between with just a push of a button. The XForce 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 turbo howl while cruising down the highway. The choice is yours.

      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 XForce Varex Cat-Back Exhaust is manufactured from high quality 3" diameter stainless steel tubing for superior durability and corrosion resistance. The System includes a Y Mid Pipe 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 XForce Varex Cat-Back Exhaust is designed as a direct fit bolt-on upgrade for the 2015 to 2020 EcoBoost Fastback Mustangs without the Active Valve Exhaust.

      Fitment: 2015 2016 2017 2018 2019 2020 Details

      XForce FM16-VMK-CBS

      CA Residents: WARNING: Cancer and Reproductive Harm -

      Installation & What's in the Box

      Installation Info

      What's in the Box

      • (1) Passenger Side Muffler Assembly
      • (1) Driver Side Muffler Assembly
      • (1) Y-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 EcoBoost

      Customer Reviews (2)

        Reviews of XForce Exhaust products have an average rating of 4.2 out of 5

          Questions & Answers

          10 More Questions

          Will It Fit My Mustang

          • EcoBoost - 15, 16, 17, 18, 19, 20

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