SLP Mustang Loudmouth Cat-Back Exhaust M31007 (99-04 GT, Mach 1)

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

100+ Reviews 16 Answers

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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 (86) Customer Reviews (100+) Questions (50) & Answers (16)

Review & Installation 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

Installation Time: (approx) 2 Hours

Difficulty Level:Light to Moderate mechanical skill required.

Installation Guides:

Manufacturer:
How to install a SLP Loudmouth Catback Exhaust on your 1999-2004 GT Mustang

Customer Submitted:
SLP Loudmouth Catback Installation Guide (99-04 GT/Mach 1)

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

Tech Guides:

How to Modify Your V6 Mustang's Exhaust - Dual Conversion & More!

Will it fit my Mustang?

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

Fits GT, Mach 1, and Bullitt

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.
It will probably sound alright at low RPM's but as soon as you get into it -- LOUD and not ricey but very 'V6'y', if you want as much low end rumble with a V6 as you can get - look into a chambered muffler or possibly the Loudmouth II series. I had a flowmaster 40 series on a V6 explorer and it sounded good and muscular without being loud and obnoxious.
100% no it will give it the sound of a v8

Helpful (1) Show 2 more answers

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

Not finding an answer? Ask your question! 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

Yes, this cat back will bolt up with your application.

Helpful (0)

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

The loudmouth 1 catback will fit up to the Pypes Catted X-Pipe (98-04 V6) as the piping is the same 2.5"

Helpful (0)

Do I need an adapter to bolt this up to my 3” Kooks Catted X Pipe? 1 answer

You would need an adapter since this is only a 2.5" system.

Helpful (0)

Will any kinds of cats work on this? 1 answer

Yes, an aftermarket and stock catalyticconverters are compatible with this exhaust.

Helpful (0)

Will this fit onto a bbk off road x pipe? 1 answer

Yes, this exhaust will work with the BBK off-road x-pipe.

Helpful (0)

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

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!

Helpful (0)

Hi will this bolt up to a Mac shorty x pipe with Mac LT's? Thanks!! 1 answer

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

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? 1 answer

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.

Helpful (0)

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

Yes, that Kooks midpipe will work with an aftermarket cat-back.

Helpful (0)

Will this bolt up to a bbk h pipe? 1 answer

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

Helpful (0)

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

no one in the world ever gets what they want, and that is beautiful

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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) Thanks for your input!
- Loudness (Volume) 5
  5
- Exhaust Note 5
  5
- Fit & Finish 5
  5
- Bang for your Buck 5
  5
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) Thanks for your input!
- Loudness (Volume) 5
  5
- Exhaust Note 5
  5
- Fit & Finish 5
  5
- Bang for your Buck 5
  5
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) Thanks for your input!
- Loudness (Volume) 5
  5
- Exhaust Note 5
  5
- Fit & Finish 5
  5
- Bang for your Buck 5
  5
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) Thanks for your input!
- Loudness (Volume) 4
  4
- Exhaust Note 1
  1
- Fit & Finish 5
  5
- Bang for your Buck 5
  5
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) Thanks for your input!
- Loudness (Volume) 5
  5
- Exhaust Note 5
  5
- Fit & Finish 5
  5
- Bang for your Buck 5
  5
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) Thanks for your input!
- Loudness (Volume) 3
  3
- Exhaust Note 3
  3
- Fit & Finish 5
  5
- Bang for your Buck 3
  3
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) Thanks for your input!
- Loudness (Volume) 5
  5
- Exhaust Note 5
  5
- Fit & Finish 5
  5
- Bang for your Buck 5
  5
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) Thanks for your input!
- Loudness (Volume) 5
  5
- Exhaust Note 5
  5
- Fit & Finish 5
  5
- Bang for your Buck 5
  5
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) Thanks for your input!
- Loudness (Volume) 4
  4
- Exhaust Note 5
  5
- Fit & Finish 5
  5
- Bang for your Buck 4
  4
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) Thanks for your input!
- Loudness (Volume) 5
  5
- Exhaust Note 5
  5
- Fit & Finish 5
  5
- Bang for your Buck 5
  5
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) Thanks for your input!
- Loudness (Volume) 4
  4
- Exhaust Note 4
  4
- Fit & Finish 5
  5
- Bang for your Buck 5
  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) Thanks for your input!
- Loudness (Volume) 5
  5
- Exhaust Note 5
  5
- Fit & Finish 5
  5
- Bang for your Buck 4
  4
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) Thanks for your input!
- Loudness (Volume) 5
  5
- Exhaust Note 4
  4
- Fit & Finish 5
  5
- Bang for your Buck 5
  5
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) Thanks for your input!
- Loudness (Volume) 5
  5
- Exhaust Note 4
  4
- Fit & Finish 5
  5
- Bang for your Buck 3
  3
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) Thanks for your input!
- Loudness (Volume) 5
  5
- Exhaust Note 5
  5
- Fit & Finish 5
  5
- Bang for your Buck 4
  4
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) Thanks for your input!
- Loudness (Volume) 5
  5
- Exhaust Note 5
  5
- Fit & Finish 5
  5
- Bang for your Buck 5
  5
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) Thanks for your input!
- Loudness (Volume) 5
  5
- Exhaust Note 4
  4
- Fit & Finish 5
  5
- Bang for your Buck 5
  5
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) Thanks for your input!
- Loudness (Volume) 5
  5
- Exhaust Note 5
  5
- Fit & Finish 5
  5
- Bang for your Buck 5
  5
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) Thanks for your input!
- Loudness (Volume) 5
  5
- Exhaust Note 5
  5
- Fit & Finish 5
  5
- Bang for your Buck 5
  5
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) Thanks for your input!
- Loudness (Volume) 4
  4
- Exhaust Note 5
  5
- Fit & Finish 4
  4
- Bang for your Buck 5
  5

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

Buy Together

$530.95

+$279.68

+$54.99

+$21.99