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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?
    • Bullitt - 01
    • GT - 99, 00, 01, 02, 03, 04
    • Mach 1 - 03, 04

    Fits GT, Mach 1, and Bullitt

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    Customer Photos (78) Submit Your Photo

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    39 Questions / 8 Answers

    Ask a Question

    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)

    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 (0)

    Will this exhaust pass the emission inspection in California?

    Daniel

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

      AMJEFF

    Helpful (0)

    Hi, my car won't pass inspection and I'm wondering if it has anything to do w the exhaust even thoug I removed my cat backs so I'm running catless with the lm1

    Khalil

    • The reason you are failing inspections is most likely due to the fact that you have removed your cats. You will have to replace your cats. Especially if you are failing based on emissions.

      AM MikeW

    Helpful (0)

    will i need to buy anything else with this to install onto a 2001 gt

    MarcusSs

    • The SLP Loudmouth Cat-Back Exhaust will be a direct bolt in install for the 2001 GT with no additional components required.

      Rob D

    Helpful (0)

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    Customer Reviews (100+) Write a Review

    Overall Rating 4.9

    out of 5 stars

    Installation Time:Afternoon

    Installation Cost:$100-$250

    • Loudness / Volume 4.79452 4.8
    • Exhaust Note 4.828767 4.8
    • Fit & Finish 4.835617 4.8
    • Bang For Your Buck 4.780822 4.8



    • 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 (0)

    • 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.

      AaronD

      Year: 2004 Submodel: GT

      Helpful (0)

    • 5/5

      Installation Time: Full Day

      February 08, 2018

      Great Exhaust

      Really nice exhaust, I was skeptical at first due to seeing other reviews saying the exhaust is "too loud". It's loud, but not to the point to where its excessive. Nice throaty distinctive muscle car sound, great system.

      Tim

      Year: 2003 Submodel: GT

      Helpful (0)

    • 5/5

      Installation Time: Afternoon

      February 08, 2018

      The name speaks for itself

      I have this catback paired with the pypes O/R H and its the loudest exhaust ive heard. Growls past 2300k RPMs. If youre pushing it.... dont expect to hear anything but the exhaust. And be sure to tell all your neighbors sorry, theyll hate you haha.

      KyleF

      Year: 2001 Submodel: GT

      Helpful (0)

    • 5/5

      Installation Time: Less than 1 Hour

      January 23, 2018

      02 Mustang Gt

      Very nice sounding, loud and backfires!! I also suggest you get shorty tuned headers and an X-pipe if you really want to shut anyone else up with a loud exhaust!

      PatrickM

      Year: 2002 Submodel: GT

      Helpful (0)

    • 5/5

      Installation Time: Afternoon

      December 09, 2017

      SLP Loudmouth

      The only thing you need to do is cut off right after the muffler and then it's straight forward from there. This exhaust has a deep aggressive tone that really wakes up the car! Would definitely recommend for someone beginning to mod their car!!

      Jason

      Year: 2000 Submodel: GT

      Helpful (0)

    • 5/5

      Installation Time: Less than 1 Hour

      December 08, 2017

      Slp

      Love this exhaust, sounds great and make my neighbors mad best mod I've done so far. Thank am

      TimothyE

      Year: 2003 Submodel: Cobra

      Helpful (0)

    • 5/5

      Installation Time: Afternoon

      December 08, 2017

      SLP Loudmouth

      I only used some driveway ramps and it was enough to get underneath to install. Was very easy to put on. The hardest part was getting the old off. When first taking off this exhaust has a deep sound and when you punch it, it screams. This is a great exhaust.

      Caleb

      Year: 1999 Submodel: GT

      Helpful (0)

    • 5/5

      Installation Time: Afternoon

      December 08, 2017

      Loud

      Had this exhaust on my foxbody years ago and now got it for my 03 Mach 1. Fitment is good and the sound is great. Super loud when you put your foot into it, but mellow when you're just cruising.

      James

      Year: 2003 Submodel: Mach 1

      Helpful (0)

    • 5/5

      Installation Time: Afternoon

      November 07, 2017

      Slp LOUD

      If you like loud then you will like these. It is what i wanted. Very pleased with the product and install. Hardest part was cutting the old off

      MichaelR

      Year: 2003 Submodel: GT

      Helpful (0)

    • 5/5

      Installation Time: Afternoon

      October 22, 2017

      Best Cat-Back

      I thought when i first bought these they might be too loud but these things are PERFECT! They make your car sound amazing, if you want your mustang to be sound better then your friend (that probably has flowmasters) get these.

      ChandlerH

      Year: 2000 Submodel: GT

      Helpful (0)

    • 4/5

      September 30, 2017

      SLP LM1

      If you want your car to sound like a race car then this is the exhaust for you. I love the sound of this exhaust it is like no other out there. it is a little on the pricey side however. and i also have it paired with the slp x pipe with high flow cats. which sounds a bit deeper rumble to the pitch. Only disadvantage is the exhaust seems to hang a little low you can always cut and modify it to have it fit better underneath, but with lower cars i would not recommend getting the x pipe to pair with this exhaust, i have 1.5 inch lowering springs and the cats sit about 2.5 inches off the ground.

      Mike

      Year: 2003 Submodel: GT

      Helpful (0)

    • 5/5

      Installation Time: Afternoon

      September 20, 2017

      Amazing sound

      These are amazingly loud and sound great. Easy and straight forward install. Recommend for any 2v for 4v out there. Perfect fit and finish

      Updog

      Year: 2004 Submodel: Mach 1

      Helpful (0)

    • 5/5

      Installation Time: Less than 1 Hour

      September 19, 2017

      nice sound!

      Took about an hour to put on....I installed it and a cold air intake...I noticed a difference in HP immediately! It is quite below 2000 rpms but when you get on it it roars.....I have a convertible and didnt want to something too loud...this is perfect!

      DavidN

      Year: 2003 Submodel: GT

      Helpful (0)

    • 5/5

      Installation Time: Less than 1 Hour

      September 17, 2017

      great tone

      sounds basically straight piped in high rpms and still has a nice rumble in low rpms , to get that overall loudness however it will need a mid pipe

      MarcusP

      Year: 2001 Submodel: GT

      Helpful (0)

    • 5/5

      Installation Time: Afternoon

      September 02, 2017

      Aggressive sound and easy install.

      The SLP Loudmouth exhaust system on my 03 GT has a nice throaty sound when going through the gears around town and on the highway. When you mash the pedal it comes alive and barks a very distinct exhaust note. Highly recommend the system coupled with the SLP catted X pipe it all went together with no hastle and in under 4 hours. It looks as good underneath as it sounds.

      TimC

      Year: 2003 Submodel: GT

      Helpful (1)

    • 5/5

      August 27, 2017

      .

      Slps have a very good sound little loud. But would recommend them to anyone

      JosephB

      Year: 1999 Submodel: GT

      Helpful (0)

    • 5/5

      Installation Time: Afternoon

      August 11, 2017

      Amazing sound

      Really wakes up your mustang.its not to loud if your just crusing but if you put your foot into it poeple definitely hear coming down the road.

      RobertU

      Year: 2001 Submodel: GT

      Helpful (0)

    • 4/5

      Installation Time: Afternoon

      August 10, 2017

      Awesome sound

      Very happy, mach 1 sounds awesome! Clamps aren't the best, I HIGHLY RECOMMEND driving around the block and then re-torquing all bolts. Very happy with the system

      Charnis

      Year: 2004 Submodel: Mach 1

      Helpful (0)

    • 4/5

      Installation Time: Afternoon

      July 27, 2017

      L O U D M O U T H

      Awesome sound... easy install with the proper tools..

      GeorgeF

      Year: 2001 Submodel: GT

      Helpful (0)

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