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

Market Price $529.95 You Save 3% ($15.00)
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$514.95

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  • Item 23001
  • MPN# M31007

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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

    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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    42 Questions / 6 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)

    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

    hi I got a 2000 mustang gt and I would like to purchase kooks headers long tube 1/3/4 and the kooks catted pipe. my question is will the kooks x pipe3 inch catted work with my sap cat back? thanks

    lora

    Will this bolt up to a bbk h pipe?

    EricG

    • The SLP Loudmouth Cat-Back Exhaust will bolt up to the BBK H-pipe yes.

      AMRickyD

    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 4.768293 4.8
    • Exhaust Note 4.804878 4.8
    • Fit & Finish 4.835366 4.8
    • Bang For Your Buck 4.75 4.8



    • 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 (0)

    • 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 (0)

    • 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 (0)

    • 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 (0)

    • 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 (0)

    • 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 (0)

    • 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 (1)

    • 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 (1)

    • 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 (4)

    • 4/5

      Installation Time: Less than 1 Hour

      March 10, 2018

      Great exhaust

      This an amazing exhaust i didnt think it was going to be nearly as loud as it actually is no video serves this kit justice.

      AnthonyA

      Year: 2004 Submodel: GT

      Helpful (2)

    • 5/5

      Installation Time: Less than 1 Hour

      March 08, 2018

      Sounds great and easy to install!

      I had my doubts about how it would sound on my mustang gt, but I am not disappointed!! It sounds amazing, and was a lot easier to install than I first thought. Great exhaust, and quickly shipped. Will definitely buy from this site again!

      Sarahg

      Year: 2002 Submodel: GT

      Helpful (2)

    • 5/5

      March 04, 2018

      INSANE!

      This thing makes that 4.6 sound like a monster! 10/10 would recommend.

      BryceB

      Year: 2003 Submodel: GT

      Helpful (3)

    • 5/5

      Installation Time: Afternoon

      February 25, 2018

      Great Product

      The fitting was perfect and only took me about 2 hours or so just because my h-pipe bolts had to be cut. My only complaint is, i wish they were a little louder.

      AlecS

      Year: 2003 Submodel: GT

      Helpful (2)

    • 5/5

      Installation Time: Afternoon

      February 19, 2018

      Slp

      I love my slp I have it with a bbk offroad x yes it’s loud but everyone loves it and it sounds amazing

      OlindoH

      Year: 2001 Submodel: GT

      Helpful (2)

    • 5/5

      February 12, 2018

      Loudmouth

      Adds an aggressive sound. Not overly loud during idle so the neighbors won't hate you too much. Definitely a good buy.

      Aaron

      Year: 2004 Submodel: GT

      Helpful (3)

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