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SLP Loudmouth Cat-Back Exhaust (99-04 GT, Mach 1)

SLP Loudmouth Cat-Back Exhaust (99-04 GT, Mach 1)
100+ Reviews 8 Answers
Market Price $529.95 You Save 3% ($15.00)
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  • Item 23001

  • MPN# M31007

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    SLP Loudmouth Cat-Back Exhaust (99-04 GT, Mach 1)

    SLP Loudmouth Cat-Back Exhaust (99-04 GT, Mach 1)
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        Features, Video & Details

        • Rich, Throaty Exhaust Tone
        • Loudmouth "Shotgun" Race Resonators Included
        • Versatile Modular Design
        • 2.5" 409 Stainless Steel Tubing
        • 3.5" Polished 304 Stainless Steel Tips
        • Fits 1999-2004 GT, Bullitt, & Mach 1 Mustangs

        Product Resources

        Customer Photos (80) Customer Reviews (100+) Questions (44) & Answers (8)

        Review & Installation Video

        Review & Install Video

        More Power and Sound.   This SLP system includes SLP's infamous Loudmouth "shotgun" race resonators that offer virtually zero flow restriction to free up more power and to produce the most aggressive sound possible.

        Modular Design.   SLP's unique modular design allows you to quickly and easily switch out the mufflers or resonators to suit your driving needs. Along with the included resonators, the Loud Mouth system is compatible with all SLP mufflers and resonators including the bullet-type Loud Mouth II and the traditional-style PowerFlo Muffler.

        Superior SLP Construction.   This SLP Cat-Back system is made from mandrel bent 2.5" 409 stainless steel tubing for for its excellent non-restrictive flow characteristics and long life. The system ends with a brightly polished 304 stainless steel 3.5" tips, that are electro-marked with the distinctive SLP logo, giving a great finishing touch and a show quality look.

        Application.   Designed to be a direct bolt on, this SLP Loudmouth catback will bolt straight up to the factory Mid-Pipe without any extra modifications required on the 1999-2004 GT, 2001 Bullitt, or 2003-2004 Mach 1 Mustang to give it a rich, throaty sound.

        Fitment: 1999 2000 2001 2002 2003 2004 Details

        What's in the Box
        Hardware included:
        • (2) Intermediate Pipes
        • (2) Over-axle Pipes
        • (2) Resonators
        • (2) Tailpipes
        • (2) Tailpipe Tips
        • (8) Clamps
        • (2) Ball Flanges
        • Instructions
        Installation Info
        Tech Specs
        Cat-Back Exhaust Specifications
        Piping Material: 409 Stainless Steel Tip Material : Polished 304 Stainless Steel
        Piping Size: 2.5" Tip Size: 3.5"
        Muffler Type: Straight-through Fitment: 1999-2004 GT / Mach 1 / Bullitt Mustangs
        Will it fit my Mustang?

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        Customer Photos (80) Submit Your Photo

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        44 Questions / 50 Answers

        Ask a Question

        Will this bolt up to a Mac off road h pipe on my 99 gt?

        ColtC

        • The SLP Loudmouth Cat-Back Exhaust will not bolt directly up to the Mac off-road H-pipe. The cat-back and the h-pipe use different couplers to connect.

          Rob S

        Helpful (1)

        Are these legal in WA

        PedroB

        • This exhaust does not affect emissions so it will pass inspection and emissions, however, depending on your local land ordinances in WA this exhaust may violate a sound ordinance if they are strict in your area.

          AMJEFF

        Helpful (1)

        Will this sound ricey with my v6 mustang? Ill be using an off road x pipe, i also have a cai and 65mm throttly body installed.

        Larryde

        • I assume you have a dual exhaust system on your V6 or are building one. Part of what you can do to help get the growl is use an H-Pipe vs an X-Pipe. It changes the harmonics up. Check out the clip and keep in mind that this is a stock GT exhaust with Factory manifold and factory h-pipe. Find an exhaust with a sound like what you're after. The SLP Loudmouth sires is just that, Loud. If you want more of a rumble, you might try the magnaflows.

          SteelWolf

        Show 2 more answers Helpful (1)

        I have a Mach 1, and I'm wanting loud! I have had a 2v with an off road X and Borla Stingers. I was going to do the same on the Mach but wondering if the SLP's are just as loud? They are 100 less so just wondering.

        BrandonK

        • This exhaust system will be just as loud but it will have a different tone than the stinger exhaust by Borla. The SLP exhaust does sound great and would definitely be a great pick!

          AMJalisaB

        Helpful (0)

        Hi will this bolt up to a Mac shorty x pipe with Mac LT's? Thanks!!

        Jeremy

        • Yes, this cat-back will work with that aftermarket x-pipe.

          AMPaulS

        Helpful (0)

        Can this setup fit a pypes o/r x pipe(99-04 V6) along with MAC Ceramic Long Tube Headers(01-04 V6) and if so would you just recommend using the MAC o/r h pipe(99-04 V6) for better fitment?

        DiegoT

        • The SLP Loudmouth Cat-Back Exhaust can be used with a Pypes Off Road X-Pipe. If using Mac Long Tube Headers, a matching Mac Shorty Mid pipe would be required.

          AMRobD

        Helpful (0)

        People Who Bought This Item Also Bought

        Customer Reviews (100+) Write a Review

        Overall Rating 4.9

        out of 5 stars

        Installation Time:Afternoon

        Installation Cost:$100-$250

        • Loudness / Volume 4.758823 4.8
        • Exhaust Note 4.805882 4.8
        • Fit & Finish 4.841177 4.8
        • Bang For Your Buck 4.747059 4.7



        • 5/5

          Installation Time: Afternoon

          July 15, 2018

          2004 GT

          You cannot find another Cat-Back exhaust system for this car for the price and performance. Very pleased with everything and installation was quick and easy. Although, to get the full sound effect of this system, a midpipe is almost necessary.

          ColeM

          Year: 2004 Submodel: GT

          Helpful (0)

        • 5/5

          Installation Time: Afternoon

          June 25, 2018

          Sound real nice

          Glad I went with these because they sound mean, very easy install!

          DavidI

          Year: 2000 Submodel: GT

          Helpful (1)

        • 5/5

          Installation Time: Less than 1 Hour

          June 04, 2018

          Awesome Exhaust

          It was easy to install, it sounds amazing at idle and went you get on it everyone turns there heads to see what's going on. I recommend anyone to make there mustang louder to get this product

          LucasH

          Year: 2001 Submodel: GT

          Helpful (1)

        • 5/5

          Installation Time: Afternoon

          May 31, 2018

          Sounds AMAZING

          Sounds really good if you like loud! I’ve had many compliments. Everyone says it sounds like a 4v and not a 2v. Unique great sounding exhaust

          DevanK

          Year: 2002 Submodel: GT

          Helpful (1)

        • 5/5

          Installation Time: Less than 1 Hour

          May 30, 2018

          Mean

          These cat back are amazing they really wake up your car. I had no trouble installing what so ever. Super easy. It took under an hour and I did it at home with no life just a drive on ramps.

          NathanE

          Year: 2003 Submodel: GT

          Helpful (1)

        • 5/5

          Installation Time: Afternoon

          May 28, 2018

          awesome

          very happy with the end result great product would recommend buying.

          GaryE

          Year: 2003 Submodel: GT

          Helpful (1)

        • 5/5

          Installation Time: Afternoon

          May 22, 2018

          Great Product.

          Worth every penny. Only took a few hrs to install and all parts fit perfectly.

          DerrickH

          Year: 2003 Submodel: GT

          Helpful (1)

        • 5/5

          Installation Time: Afternoon

          May 22, 2018

          Slp loudmouth

          I am very pleased with this exhaust,it has a rich throaty sound and that's what I was looking for! I couldn't be happier!

          Gmanrocks

          Year: 2004 Submodel: GT

          Helpful (1)

        • 1/5

          May 21, 2018

          Defected part!

          Everything was great until the driver side went on. The tailpipe end that connects to the over axle pipe were the same diameter. The tailpipe end should of been wider but it wasn't and the bracket for the muffler broke..So I had to spend $200 to get the pipes welded...Highly disappointed and I talked with an americanmuscle rep and they wanted me to ship the whole exhaust back and get a new one or order a new one take the one piece out and send it back for a refund...which makes no sense at all..I was not going to have my car down for 2-4 weeks as I am working overseas....

          edwardd

          Year: 2004 Submodel: GT

          Helpful (2)

        • 4/5

          Installation Time: Less than 1 Hour

          May 15, 2018

          SLP loudmouth

          Fit was great easy also and was quick to put on.The sound is amazing good for your money best purchase

          RobertS

          Year: 2004 Submodel: Mach 1

          Helpful (1)

        • 5/5

          Installation Time: Afternoon

          May 15, 2018

          Very nice system

          The product has a very clean look and a nice rumble at 2k rpm but if you want it to be loud would highly suggest getting a X pipe.

          BrendenD

          Year: 2004 Submodel: GT

          Helpful (1)

        • 5/5

          Installation Time: Afternoon

          May 12, 2018

          Slp catback

          Slp has brought beast mode out of my 04 stang. I really like my slp loudmouth, even though my neighbor's not so so much!!!

          CharlesS

          Year: 2004 Submodel: GT

          Helpful (1)

        • 5/5

          Installation Time: Less than 1 Hour

          May 06, 2018

          Very Loud!

          This exhaust is very loud and sounds great. Definitely a noticeable difference from the factory flow masters.

          AngelR

          Year: 2001 Submodel: GT

          Helpful (1)

        • 5/5

          Installation Time: Less than 1 Hour

          May 02, 2018

          Catback

          They sounded good when I put them on with my stock hpipe but when I threw on the off road hpipe it sounds like a race car no lie. Sweet set up if you like it loud.

          HarrisonP

          Year: 2004 Submodel: GT

          Helpful (1)

        • 5/5

          April 27, 2018

          Loud, Crisp, No rattle, fits perfect!

          I dont know why people have had issues with the clamps, they seemed to work perfectly fine. Everything fit very well and the clamps just made it a quick and easy process. I got the whole thing done in about an hour with a lift, since with a jack these would be an absolute pain. The sound is insane! My long tube headers and off road x pipe really make these scream!

          MichaelS

          Year: 1999 Submodel: GT

          Helpful (2)

        • 5/5

          Installation Time: Shop Install

          Installation Cost: $100-$250

          April 12, 2018

          Rooooar

          Man O Man are these bad boys nasty!! I didn’t even need new pipes cuz I already had some aftermarket ones on the car. But I ordered these and she growls like a beast!! That 3.5 in tip makes that rear end look really good

          TayR

          Year: 2002 Submodel: GT

          Helpful (1)

        • 5/5

          Installation Time: Less than 1 Hour

          April 02, 2018

          Bassani Catted X SLP LM1

          Install was a breeze. All parts fit perfectly; extremely impressed that the tailpipes came in two pieces which allowed for optimal alignment. I did use a lift, also used an exhaust jack to keep it all in place while cinching everything down. Is it loud? Yeah. But thankfully with the high flow cats - it prevents the annoying popping sound under acceleration that you'll hear from people going with off road exhaust, or if they're using a sub-par quality midpipe. Expect a slightly deeper tone on start up, the sweet spot is right around 2400 RPM - 2800 RPM and then obviously WOT is amazing too. I've had plenty of people stop, flag, and ask what I'm running. You will not be disappointed.

          ATU14

          Year: 2004 Submodel: Mach 1

          Helpful (2)

        • 5/5

          Installation Time: Afternoon

          March 29, 2018

          Cobra loudmouth

          I was a little worried about it being too loud with my off road Mac Pro chamber but it actually sounds amazing. My neighbor’s hate me but I also get a lot of compliments. It’s deep but absolutely scream’s when you get on it even a little. Overall it’s an amazing exhaust system. Would definitely recommend to anyone. Thanks American musle for Quik delivery.

          LynxT

          Year: 2001 Submodel: Cobra

          Helpful (1)

        • 3/5

          Installation Time: Less than 1 Hour

          March 20, 2018

          Great sound horrible clamps

          Quick and easy install on the lift took about 20 mins to install tightened everything down and headed Dow the road exhaust fell apart due to the clamps not clamping so I bought the good clamps and haven’t had a problem figured for the money u spend you would get all quality stuff but not true

          KevinS

          Year: 2000 Submodel: GT

          Helpful (2)

        • 5/5

          Installation Time: Afternoon

          March 16, 2018

          Glad I went with the SLP LM1

          I am pretty pleased with the LM1 system. I went back and forth for a while on which system to get. I wanted something louder than the Spintech catback I was running, but I didn't want something too raspy or obnoxious sounding. I was nervous because I know the LM1 can sound pretty raspy sometimes. However, I find that most of the time when they sound raspy it is when they are paired with an off-road x-pipe. I am running Bassani mid length headers, a Bassani x-pipe with one set of high flow cats, and now the LM1 system. It sounds great. Not too raspy at all. Nice tone and noticeably louder under acceleration than my last catback. Fit and finish was nice. One thing I particularly liked was the modular design of the system. It allows for a great deal of adjustability. This ended up being more important that I though because of the panhard bar I am running. It is a tight squeeze getting the pipes to clear the axle, fuel tank, and the panhard bar. This system allowed for more points of adjustment than most systems would. I was able to get it in without any clearance issues. It was extremely close, but it worked great.

          Blown4valveGT

          Year: 2002 Submodel: GT

          Helpful (6)

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