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Flowmaster Outlaw Cat-Back Exhaust with Black Tips (18-20 GT w/o Active Exhaust)

Item 404856
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      Review & Installation Video

      Hey, guys. Adam here with, today we're taking a closer look at, installing and listening to the Flowmaster Outlaw Cat-Back Exhaust with Black Carbon Fiber Tips available for all 2018 and newer Mustang GTs without active exhaust. Like you heard from our sound clips a minute ago, this guy is gonna get five out of five on our loudness meter. It's exactly what we expect from a Flowmaster Outlaw. They're known to be extremely loud systems in the category. The Outlaw is essentially a straight pipe, so that's really gonna contribute to the sound you just heard. It's loud, it's raspy, and it can be ear piercing at wide-open throttle. If you're looking for all-out volume, this is a great way to go. It's got a resonator delete Flowmaster Scavenger X-pipe which is gonna help boost airflow efficiency. It's gonna give you a small bump in power and it's gonna give you a louder raspier tone than a resonator or even an H-pipe.The rest of the kit here is 409 stainless steel, middle of the road quality materials, aluminized 409 and then 304 being top quality. So, it is gonna be more corrosion and rust-resistant than aluminized, they maybe not so much as 304. And that's gonna be reflected in the price tag. A lot of the 304s is coming around 1,600 bucks, this guy's coming in around 1,200 bucks. So, it's great for the guys looking to save on a full cat-back system. The mufflers back to the tips are powder coated in black to even boost its durability there. Now, the rest of the system also is 3-inch mandrel bend tubing, 3 inches larger in diameter, and it's also mandrel bent to help reduce any kinks and airflow restrictions. The tips here are black carbon fiber. Now, not everybody likes carbon fiber. So, if you're not really interested in that there's a ton of other color options in the category available for you. Carbon fiber is very unique looking, I think it blends in really well with this we're valance, I actually really like it against our orange Fury '19 here as well. Now, these sleeves are essentially bolted to the actual materials here. The bolts are not very obvious, they're really subtle, which is not something you can say for some of the other brands in the category. So, I do like that. It's got double-walled fitment around the edges here so it's nice and thick, really aggressive looking. Personally, I think it looks pretty good. The tips are angled a little bit. Not everybody would like that, not all the systems are like that as well. So, something to keep in mind, I personally think it looks pretty aggressive.The install is gonna get three out of three wrenches on our difficulty meter, it does require cutting and some specialty tools. Now, the cutting is fairly simple, I'm gonna walk you through that process. Essentially we're gonna unbolt the entire factory cat-back in one piece and then just cut off the remaining pipe right behind the factory catalytic converters, so it is reusing those factory cats. Now, that I'm gonna use a Sawzall, I'm also going to use a die grinder just to clean up the cuts and then we'll bolt up the new system right from there. I'm gonna walk you through a whole process, it'll take you about three hours from start to finish, let's get started. Tools used in this install include an impact gun, 3/8 ratchet, an extension, short and deep 13-millimeter sockets, 15-millimeter deep socket, tape measure, sharpie, a die grinder or something similar to clean up or deburr the exhaust cuts, Sawzall with a thin curved metal blade, WD-40 or something similar and a mallet.All right, guys once you have your Mustang up in the air and supported properly whether it be on jack stands or on a lift like we have here, you wanna grab an impact gun or a ratchet and a 15-millimeter deep socket and we're going to loosen up the two band clamps holding on your factory cat-back to the catalytic converter pipes. Now, you'll see that right in front of the factory resonator, there's two nuts here and two nuts there, you don't have to completely remove them, just get them nice and loose.All right. The next step we're gonna move back toward the rear of our vehicle right under the rear subframe. Now, if you look at your rear sway bar straight past them are two hangers where your exhaust is hooked on and bolted to that subframe using two 13-millimeter bolts. From here instead of trying to slide our hangers out of the isolators, I'm actually just gonna completely unbolt the isolators to make life a lot easier. So, grab an extension and a 13-millimeter deep socket and what I like to do is go straight over the sway bar and remove those two bolts. All right. Now what I'd like to do after the bolts are removed is we have to unclip the isolator from the frame, they're still hooked in there. So, what you're basically gonna do is lift up on them so they disconnect and rotate them down and out of the way.All right. Our next step here is to get our entire factory cat-back off of the vehicle. We're gonna start up here with our resonator right in front of those, I'm gonna tap out the factory band clamps, I got my buddy Stan helping me get this thing down. If you're working on the ground, you may be able to do it by yourself, but if you're in the air, you might want a helping hand. All right. So, now we should slide them out of the hangers at the tips and they should come free. Good.So, we got your factory exhaust off of our '19 GT and we have it on the ground next door for Flowmaster Outlaw. Let's talk about some similarities and differences between the two kits starting at the front of the vehicle. Now, the factory system has this resonator mid-pipe, your Flowmaster Outlaw is a resonator delete. It also has the Scavenger X-pipe from Flowmaster which is gonna help promote a better airflow, it's gonna help promote more air coming in and overall that's gonna translate to a better power gain. Now, as you can see, it is laid out a little bit differently than your factory exhaust here, it splits out a lot wider than the factory. That's because we do have to cut those excess pipes right under the factory catalytic converters, which we'll get to in just a minute. Do note that the entire system here is 409 stainless steel, so it's the middle of the road when it comes to quality. There's the aluminized, 409 and then the more expensive 304 stainless. 409 is gonna be a little bit more corrosion and rust-resistant than aluminized steel, so it is a good way to keep costs down while still getting a better quality construction. If you're located in wintry weather areas, like I said earlier, seeing a lot of road salt, things like that, 409 is gonna hold up a little bit longer than aluminized, maybe not as long as 304, something to keep in mind. The system here is a 3-inch mandrel bent tubing. It's a little bit larger in diameter than the factory which is about 2.75 inches. So, you're getting a lot more volume of airflow moving through too which can help with power.Moving on, you can see the rest of the kit here it looks very similar. The bigger difference here comes in at the mufflers. Your factory mufflers are pretty big, lots of baffling, keeps drone down, but it's also minimizing a lot of that sound. If you're looking for sound, the Flowmaster Outlaw is essentially a straight pipe. It has these very, very small Bullitt-style mufflers, which has very little to no baffling on the inside, making it that straight-through technology, which is essentially just gonna make all-out noise and that's what we heard from our sound clip too. Now, because of that, and the fact that there is no resonator, the essential straight pipe design here is going to produce some drone inside the cabin. That's just something you can expect with what is essentially the straight pipe. So, we know that the factory muffler is giant In comparison, it's got a lot of baffling on the inside to help keep drone down while also making sure that it is aggressive but it does affect volume. If you're looking for all-out volume, I can't think of anything more raspy, and obnoxious, and loud, and aggressive and in your face than a straight through pipe design which is essentially what you're getting with the Flowmaster Outlaw. The baffling here on the inside of these Bullitt-style mufflers are virtually non-existent, there's very little to no battling in there which is gonna help produce a lot of volume and a little bit more rasp than you get with some of the other options. As a result of essentially a straight pipe you are gonna get some drone inside the cabin but if you're looking for all-out noise, and that's what you want, you definitely get that here. The black powder coating as you can see is only on the muffler and right next to the tips there. The powder coating is gonna beef up the corrosion and rust resistance at this section. A hole in your muffler or rust in your muffler can drastically affect the sound of an exhaust. So, having those a little bit more protected than the rest of the system does make a little sense, which is something that you'll see here in the Flowmaster kit. The black powder coating is gonna hold up over time and it's gonna hold up with the exhaust heat as well. Exiting out the rear it is essentially a black carbon fiber tip which has a nice sleeve bolted to the bare exhaust material. It's about 4 inches in diameter as opposed to your factory 3-inch. It's not slash-cut as deep as the factory exhaust, it's a little bit more evened out, but it does have a slight angle to it. It's a lot thicker and more aggressive-looking and it has that slightly exotic feel to it with the carbon fiber finish. And finally, the Flowmaster name there in a grayish what looks more like a frosted color.Now, there is a couple of things we need to do in preparation for install, we are gonna have to swap over the factory hanger isolator as you see here. We'll put them on our new hangers on the Flowmaster kit. So, what do you say we get started?Now, when it comes to swapping over these hanger isolators, I do find it easier to use PB B'laster and just lubricate the inside there because it can get a little tough to get off. If we just hit both sides here and inside to make life a little easier for us. I'm gonna work this guy around, as you can see, slides right off. Now, swapping these over to the Flowmaster kit you'll notice the first thing is that the hangers are facing the opposite direction. That's okay, that's how the Flowmaster kit is built. What matters is the way that the hanger isolator is facing. Take note of this tab at the top, make sure that is facing the front of the vehicle. So, opposite side of the tips. Slide that on, just rotate it down and out of the way, same thing on the other guy. Take the tab, face it the opposite direction of the hangers and how we can move on.All right, with the factory cat-back out of the way the next step here is to measure in preparation for our cut. Now, we do have to cut off these extension pipes right behind the factory catalytic converters. This system does reuse the factory cats, so we're gonna measure 11-inches from the base weld of the catalytic converter back into the piping. I'm gonna mark that with a sharpie, I'm gonna double-check that to make sure it's good, always measure twice cut once. Once we have that determined we'll be able to cut this pipe off. So, we're really cutting off about this much but it is necessary. So, grab your measuring tape, measure from the back here 11 inches, and we're gonna make our mark. All right. Now, when I say measure from base weld that's not this guy here, it's the base of the cat. So, this weld here at the bottom of it, I'm gonna measure right from the bottom out 11 inches, grab my sharpie. So, 11 inches is gonna be right about here. That's gonna be where we make our cut. Now, like I said, measure twice just to make sure you have it right, 11 inches, and I'm gonna measure on the other side, and then we can cut.Now, looking at the other side, you'll notice that there's a clamp. This pipe here is clamped on separately, in theory, we could just remove that and be okay. This marker here is actually 11 inches. So, let me show you that right now. So, I' measuring from the base, you can see 11 actually ends right where this pipe ends. You can't just remove that, we do still have to cut. If we just remove the piping, there'd be about two to three extra inches of pipe that we don't want there. So, we do still need to cut right at that line. So, I'm not even gonna use my sharpie, I'm just gonna use the end of that pipe as a reference. All right. So, I'm gonna make this cut using a Sawzall and a thin curved metal blade. You wanna make sure when you're cutting you are using a metal blade. I'm also gonna wear safety glasses, of course, you wanna be safe when you're doing this, so don't forget that step. Now, keep in mind, we are very close to the vehicle's floorboard. You don't wanna push this all the way up, because then our blade is just jabbing right into the floorboard, which obviously is not something we want, we don't wanna cause damage to anything else. So, I'm gonna have to pull back a little and let's just cut this off. And as you can see, once I cut it, this pipe is gonna fall. So, just keep that in mind. If you're working on the ground, just stay out of your way, make sure that doesn't fall on you.All right, so we have that off. I'm gonna take a die grinder and I'm gonna just deburr that to make sure it's a smooth surface. All right. So, now again, we're just repeating on the other side and I'm using the end of this pipe as a reference since that is our 11-inch mark. All right. So, now I'm gonna use my die grinder, my air tool here, it's got some fine-toothed sandpaper on it. So, I'm just gonna clean up the edges here, make sure it's ready for install. All right, same thing on the other side. All right, now we can start installing.Next up, grab your Scavenger X-pipe from Flowmaster, put your smaller two and a half inch clamps over the sides. We're going to insert that into the pipes that we just cut. All right. So, we do want this to seat back a little bit more. So, what I'm gonna do is take my mallet, I'm going to tap right here, get this guy to push right back in. Grab your 15-millimeter socket, rotate the clamps into position and tighten them down. Now, our next pipe here, I'm going to start on our driver side, we have one of the larger clamps over the end, the 3-inch clamp, where it has the slit, that'll go into the X-pipe. You wanna make sure you're picking the pipe here that has a sharper bend and a shorter ending. There's one with a longer side, that's gonna be your passenger. I'm gonna slide this kind of position. All right, now I'm gonna tighten up this clamp, get it nice and snug. Now, when I do this, I wanna leave a little bit of room for adjustment. So, I am just gonna get it snug, not too tight. All right, so now we can still rotate it if we need to. All right, same thing on the other side.All right. Now, before we move on to installing the tips and the tailpipes with the muffler, I'm actually gonna unbolt the factory isolator that our tailpipe tip hanger would hook into. These are two 13-millimeter bolts, one is facing straight down, one is facing the side. I'm gonna use the impact gonna for the bottom one. Now, for the side, I'm gonna switch over to a ratchet and get that other guy off. This will make life a lot easier for installing our tailpipes. So, I have a 3/8 ratchet and 13-millimeter short socket to get the side guy off.So, now looking at our passenger side tip, I'm gonna slide this guy on in the same direction, I'm gonna let it dangle for now, we can install this whole pipe assembly and then hook this guy back up to the frame. All right, now with the clamp in position, I'm going to hook the pipes together and then we're gonna bring this whole assembly up to hook it into our subframe. All right, so what you'll see us do is rotate this hanger up and reconnecting to our subframe. I've got that factory 13-millimeter bolt for this isolator, I'm gonna put that guy in just hand tight for now. We'll come back and tighten it down once everything's hooked up. Now what we're gonna do is lift the whole tailpipe assembly up, I'm gonna put the factory 13-millimeter bolt back in. That actually hooks right back in as well, put the bottom one in, tighten them down, and then our clamp. Now, I'm gonna use my impact gun and 13 deep socket to tighten down the bottom one and a ratchet for the top one. All right. So, now we're coming back to this clamp that connected our tailpipe to the rest of the system. I'm just gonna get a nice and snug, I still wanna leave room for adjustment. All right. So, now we're just repeating for the other side, we're going to remove this isolator and repeat that process.All right. Now we can install our tailpipe. All right. Now I'm gonna put that factory 13-millimeter bolt in position on the subframe just hand tight for now. All right. So, now I'm gonna rotate the tip hanger isolator assembly up into the frame, hang it up and put our bolts through. Back at our tailpipe clamp, we're just gonna get it nice and snug. Now we can tighten up the 13-millimeter bolts holding the hangers to the subframe.All right. So, at this point we have everything installed and as you can see the tapes do need a little bit of an adjusting. So, what we're gonna do is go back and tighten down all of our clamps making sure that it's aligned as we do so, and then we'll be good to go.That's gonna wrap up my review and install for the Flowmaster Outlaw Series Cat-Back Exhaust with Black Carbon Fiber Tips available for the '18 and newer Mustang GT without active exhaust. You can pick yours up right here at

      Product Information

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


      • Aggressive Exhaust Tone
      • Enhanced Throttle Response, Power and Gas Mileage
      • 409 Stainless Steel Mandrel-Bent Tubing
      • Black Powder-Coated Mufflers
      • Scavenger X-Pipe
      • Four-Inch Carbon Fiber Quad Exhaust Tips
      • Easy Installation
      • Lifetime Limited Warranty
      • Fits All 2018-2020 Ford Mustang GT Models without Active Exhaust


      Most Aggressive Unit. Dyno-Tuned for maximum performance, the Flowmaster Outlaw Cat-Back Exhaust steals the show by producing a high-performance exhaust system that produces an aggressive tone inside and outside your Mustang's cabin. This racing-based exhaust system was designed for the true lovers of this exhaust sound and carries the stamp of being Flowmaster’s most aggressive sound unit.

      Loud Specs. The Flowmaster Outlaw series delivers a 3-inch cat-back exhaust system that produces an aggressive exhaust tone for an enhanced throttle response, power and gas mileage. The unit comes crafted from 409 stainless-steel, mandrel-bent tubing and features scavenger X-pipe and 4-inch carbon fiber quad exhaust tips.

      Installation. This exhaust system calls for an easy installation and includes all the necessary parts and hardware for a secure and lasting install.

      Warranty. Flowmaster, Inc. offers a lifetime limited warranty on this stainless-steel product against all manufacturing defects in materials and workmanship. Please refer to the manufacturer’s website for further information and details.

      Application. The Flowmaster Outlaw Cat-Back Exhaust is designed to fit all 2018-2020 Ford Mustang GT models without Active Exhaust.

      Fitment: 2018 2019 2020 Details

      MPN# 817808

      CA Residents: WARNING: Cancer and Reproductive Harm -


      Customer Reviews (10)

      Write a Review

      Ratings Summary

      4.5 out of 5 overall rating from 10 customers

      Installation Time: Afternoon

      Installation Cost: 0-$100

      • February 08, 2020

        5 2019 GT - JonathanP Installation Time: Afternoon

        Fantastic Exhaust!!!

        This is a fantastic system! I had a Flowmaster Outlaw cat-back exhaust on my 2013 Mustang GT as well. If you really want to unleash the full potential of your exhaust, if you want to hear your Mustang roar, not just growl... ROAR! Then this is the exhaust for you. It is loud and commanding on the road and definitely turns heads. I would highly recommend this.

        Helpful (1)
      • January 28, 2020

        5 2018 GT - Brennan Installation Time: Shop Install Installation Cost: 0-$100

        Wicked Exhaust

        Insanely fierce, aggressive exhaust. If you live anywhere with noise by-laws, do not purchase. I'd wager money that louder cat-back exhausts are few and far between. Can be annoying for passengers on highway drives. Neighbours will hate you.

        Helpful (1)
      • April 04, 2019

        5 2018 GT - DirtyLew

        Explosive sound

        Much more than I imagined. The original exhaust had great sound if you like the gentle roar of a kitten. Where the outlaw series gives that serengeti wild roar of a male lion ready to do battle. There is a slight drone at 1700 RPMs but you get used to it. Another thing I love is waking up my uptight neighbors with a cold start at 0500 in the morning. Gotta love it

        Helpful (4)
      • March 05, 2019

        2 2018 GT - CodyP Installation Time: Weekend

        Didn't fit right

        They sound amazing but since they didn't slide over the old pipes at all. Took about 2 days to get it right. Very much of a drone around 2000 rpm.

        Helpful (4)
      • December 28, 2018

        5 2018 GT - JonathonM Installation Time: Afternoon


        The outlaw Cat-Back is what it is, outlaw. For those of you looking for "outlawish" sound, this is it. Stupid loud, great exhaust note, and fits like a glove. The best thing is you get a nice low growl on low RPM but that nice natural rasp of a 5.0 coyote in the upper range. There is Some drone around 2000 RPM on the highway but overall I recommend it to everyone who wants to be heard!

        Helpful (6)
      • October 24, 2018

        5 2018 GT - TimothyN Installation Time: Less than 1 Hour

        Love it

        Oh my gosh!!! I love this exhaust system. You can hear me coming!!

        Helpful (10)
      • August 22, 2018

        4 2018 GT - RyanC Installation Time: Afternoon

        Amazing sound

        This product is fantastic simply said. The only thing keeping it from a 5 star review is that my exhaust came damaged. Maybe if American Muscle used a different shipping company. Other than that, I'm very satisfied. Also it need ed to be cut a few times before it fit properly.

        Helpful (8)
      • August 21, 2018

        4 2018 GT - May Installation Time: Less than 1 Hour


        Very satisfied. A tip came out cracked, but other than that the installation was fast and it sounds amazing.

        Helpful (7)
      • July 30, 2018

        5 2018 GT - Lori Installation Time: Afternoon

        Nice look with my black rims

        The sound is very throaty. I love the black carbon fiber look with the lightning blue mustang. This definitely looks awesome with the black out look I'm going for.

        Helpful (8)
      • June 22, 2018

        5 2018 GT - Antoeknee Installation Time: Less than 1 Hour

        Sounds great

        Instructions were clear and it sounds great couldnt ask for more

        Helpful (9)

      Questions & Answers (5 answers)

      5 Top Rated Questions

      For the quad tips, your clip and build master shows them being interchangeable. Do you folks here at American muscle also sell the different tip styles or is that something you have to go to flowmasters website for? Thank you

      I have a 2018 GT Base model with this flow master outlaw cat-back exhaust what headers would be a perfect fit ? Because when i tune my cart i don't want to have any issues but i want to know what headers would be a perfect fit with this Exhaust. I also have a JLT CAI please advise ! Thank you once again you guys are the best !

      Hello american muscle! Would i have to tune this ? What the difference from the Corsa an this? Different gain of HP ? How much HP can i get out of this ?

      Is there anyway to install this with no cuts? I want this exhaust so bad for my 2019 mustang gt (without active exhaust) but I do not want any cuts. I do not think there is a catback that will sound like the outlaw does.

      • This cannot be installed without cutting.

      Helpful (0)

      I love this exhaust, but I'm afraid it will be so loud that it would catch too much unwanted attention. So I guess my question is, is this loud or is it ear shattering annoyingly loud?

      • This will be a very loud and aggressive exhaust note. We would advise that when it comes to sound it is all personal preference and to check out additional sound clips on Youtube.

      Helpful (0)
      Post Your Question

      Installation & What's in the Box

      Installation Info

      What's in the Box

      • (1) Scavenger Assembly
      • (1) Left Mid Pipe
      • (1) Right Mid Pipe
      • (1) Right Muffler Assembly
      • (1) Left Muffler Assembly
      • (4) Large Exhaust Clamps
      • (2) Small Exhaust Clamps

      Will It Fit My Mustang

          Related Mustang Categories