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

Market Price $569.95 You Save 7% ($39.00)
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$530.95

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  • Item 23001

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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

    MPN# M31007

    CA Residents: WARNING: Cancer and Reproductive Harm - www.P65Warnings.ca.gov

    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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    Questions & Answers (50)

    5 Top Rated Questions

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

    • 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.

    Helpful (4)

    Are these legal in WA

    • 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.

    Helpful (2)

    Will this exhaust pass the emission inspection in California?

    • The SLP Loudmouth Cat-Back Exhaust will not alter emissions and therefore will not cause your Mustang to fail emissions.

    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.

    • 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.

    Helpful (1) Show 2 more answers

    Will this hook up to a pypes off road x pipe?

    Post Your Question
    10 More Questions
    Will this cat back exhaust bolt onto a 2003 ford mustang gt automatic transmission with a MAC off road x pipe? 1 answer
    I have a 2004 v6 and I purchased a pypes catted X-pipe, will I have any problems fitting the loudmouth 1 catback to the pypes catted X-pipe? If so what changes would I need to do 1 answer
    Do I need an adapter to bolt this up to my 3” Kooks Catted X Pipe? 1 answer
    Will any kinds of cats work on this? 1 answer
    Will this fit onto a bbk off road x pipe? 1 answer
    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. 1 answer
    Hi will this bolt up to a Mac shorty x pipe with Mac LT's? Thanks!! 1 answer
    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? 1 answer
    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 1 answer
    Will this bolt up to a bbk h pipe? 1 answer

    Recommended For You

    Customer Reviews (100+) Write a Review

    Overall Rating 4.9

    out of 5 stars

    Installation Time:Afternoon

    Installation Cost:$100-$250

    • Loudness / Volume 4.751269 4.8
    • Exhaust Note 4.781726 4.8
    • Fit & Finish 4.842639 4.8
    • Bang For Your Buck 4.746193 4.7



    • 5/5

      Installation Time: Shop Install

      Installation Cost: $100-$250

      March 13, 2019

      BEST EXHAUST BY FAR!!!!

      I know there are a lot of exhausts to choose from, and brand names with great reviews, however, I took a shot on this one. I was NOT disappointed!! I had flowmasters on the car previously, and the difference was night and day with the new LM1's installed. I got a slight power gain, but the sound is second to none. It is a BEAST!

      TylerG

      Year: 2004 Submodel: GT

      Helpful (0)

    • 5/5

      March 05, 2019

      SLP LM1’s

      Change the sound of my 01 GT completely, good combo with my Mac longtubes and Mac off road prochamber !

      Izzy

      Year: 2001 Submodel: GT

      Helpful (0)

    • 5/5

      Installation Time: Shop Install

      Installation Cost: 0-$100

      February 27, 2019

      SLP Loudmouth

      Great exhaust, sounds awesome! Even with the factory h-pipe its got some real attitude. I love it. Thanks American Muscle!

      Xkxp017

      Year: 2001 Submodel: GT

      Helpful (0)

    • 5/5

      Installation Time: Less than 1 Hour

      February 18, 2019

      Good

      Good sound easy to install would recommend to anyone.

      David

      Year: 2001 Submodel: GT

      Helpful (0)

    • 5/5

      Installation Time: Less than 1 Hour

      February 07, 2019

      Nice and loud

      Sounds amazing with the o/r x pipe nice and loud sure woke up the car and neighbors

      RigobertoC

      Year: 2003 Submodel: Mach 1

      Helpful (0)

    • 5/5

      January 28, 2019

      Slp

      You at AMerican muscle are great I will be ordering more parts

      GordonB

      Year: 2004 Submodel: GT

      Helpful (0)

    • 5/5

      Installation Time: Afternoon

      December 19, 2018

      SLP Loudmouth 1 - Everything I expected

      I wanted to upgrade the stock exhaust and after doing tons of research I decided to purchase the SLP Loudmouth 1. The sound is great. I wanted something louder but not too loud and with the stock cats, just what I wanted. Later I'll do other upgrades to make it even louder. Installing was not too difficult. I had to mess with the alignment but other than that it was pretty straight forward. Highly recommend.

      Eli

      Year: 2002 Submodel: GT

      Helpful (4)

    • 5/5

      Installation Time: Afternoon

      December 17, 2018

      Great MFing product

      This product is bangin loud and easy to install if your an experienced mechanic as myself. The best exhaust on the market, no problems putting in. Solid product.

      BrentS

      Year: 2002 Submodel: GT

      Helpful (2)

    • 5/5

      Installation Time: Less than 1 Hour

      December 04, 2018

      SlP Review

      Great sounding exhuast best one you can buy for a decent price!

      JaimeF

      Year: 2002 Submodel: GT

      Helpful (2)

    • 5/5

      Installation Time: Less than 1 Hour

      November 09, 2018

      SLP LM1

      Greatest addition to my already monsterous set up. Kooks Long Tube Headers, Kooks Catted X Pipe and then the SLP LM1

      MikeM

      Year: 2002 Submodel: GT

      Helpful (3)

    • 5/5

      Installation Time: Afternoon

      November 02, 2018

      Loudmouth describes it

      Exhaust sound mean down low and rips your heart out 3k rpms. Sounds super aggressive when accelerating and is nice and mild when calming cruising down the highway. I installed with the stock catted mid pipe and the combo is perfect. You can be super loud when you want and tame when driving like grandma. I eventually plan to do the off-road x pipe also because im an obnoxious 20 year old:)

      BlakeM

      Year: 2002 Submodel: GT

      Helpful (5)

    • 5/5

      Installation Time: Afternoon

      October 25, 2018

      Loud Proud

      Great craftsmanship easy to install even with no lift. I would give 5 stars.

      John

      Year: 1999 Submodel: GT

      Helpful (3)

    • 5/5

      Installation Time: Afternoon

      October 11, 2018

      Easy

      It was easy to install. Only took a couple hours doing it by myself in the garage with hand tools. I had to use a couple extra jack stands to hold everything while I bolted everything. Overall great sound over stock.

      JeremyV

      Year: 2001 Submodel: GT

      Helpful (3)

    • 4/5

      Installation Time: Afternoon

      October 04, 2018

      Good quality, unique sound

      Lets start with fit and finish. I had to replace my pype bombs after my car rolled into a fire hydrant. The SLP fit much, much nicer and the 2 piece over the axle makes installation a breeze. The resonators (2 1/2 inch pipe ending inside larger pipe, no baffles or anything whatsoever) are polished and the tips are just sexy. Now for sound, this is definitely different from most exhausts. I also installed an offroad h pipe at the same time. If youre very gentle on the loud pedal and keep it under 2k its quiet. In fact, constant speed cruising its almost silent. But you give her the beans, and its like the devils orchestra starts playing. Sooo loud and angry, clear from 2k to redline. You better look for cops close before getting into it. And neighbors? Yeah, they now hate you for certain. And if there was a sound clip in the dictionary under "raspy", this would be it. It resonates really effin loud at certain rpms. On decel, she pops and gurgles, and at some rpms is almost as loud as when youre on it. If youre looking for the loudest, raspiest, rawest exhaust sound possible, look no further. Its not for everyone, and the second i get a noise ticket ill be switching to lm2s or installing cats. Lol.

      TrestonH

      Year: 2002 Submodel: GT

      Helpful (7)

    • 5/5

      Installation Time: Less than 1 Hour

      October 04, 2018

      SLP loudmouth

      Replaced my Borla system with the SLP and love it. Not that the Borla was a bad system by any means but the SLP has a deeper base note and more rumble/crackle which I like. Not overly loud at idle, nice purr out on the highway yet balls loud when u get on it a win win all the way around with the Loudmouth.

      MarkD

      Year: 2004 Submodel: GT

      Helpful (3)

    • 5/5

      October 01, 2018

      Loud

      Adds plenty of volume for a low price, best purchase so far!!

      BKC15

      Year: 2003 Submodel: Mach 1

      Helpful (3)

    • 5/5

      Installation Time: Afternoon

      September 25, 2018

      loud

      very loud if you are looking for for loud exhaust.

      NasserT

      Year: 2001 Submodel: GT

      Helpful (3)

    • 5/5

      Installation Time: Shop Install

      Installation Cost: $100-$250

      September 23, 2018

      GREAT SOUND...

      THEY ARE GREAT...I HAVE BETTER GAS MILEAGE...BETTER ACCELERATION...

      KenW

      Year: 2003 Submodel: GT

      Helpful (3)

    • 5/5

      Installation Time: Shop Install

      Installation Cost: $250-$500

      September 20, 2018

      Release the beast

      Hello to all you Mustang enthusiasts I was really excited about installing a loudmouth cat back exhaust and also included the catted SLP X pipe wow I have to say this the sound my car makes now incredible if you want to release the Grrrrr in your Mustang GT or Mach 1 I highly recommend the SLP exhaust systems they have to offer. Ride hard and loud! happy motoring .

      KenG

      Year: 2003 Submodel: GT

      Helpful (4)

    • 5/5

      Installation Time: Less than 1 Hour

      September 12, 2018

      SLP Loudmouth

      I'll get straight to the point. This is the best axle back exhaust setup for an 03-04 Mach 1 that I've ever experienced. No other brand can compare to the majestically powerful soundtrack these resonators create. To anyone who thinks that just this without an aftermarket X or H pipe isn't enough, save your money, trust me its loud enough. Had my favorite shop install them in 40 minutes no problem. The welds are fantastic and the SLP engraving on the tips adds a nice touch. Worth every penny. Just buy them. P.S.- To all other Mach 1 owners, it may just be me but on deceleration i get a good bit of crackles and pops. Sounds super cool. Stock headers and factory H pipe.(must be a 4 valve thing.)

      JordanB

      Year: 2003 Submodel: Mach 1

      Helpful (3)

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