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

68 Reviews
Our Price

$517.95

  • Item #23017
  • MPN# M31007A

  • Market Price $539.95
  • You Save 4% ($22.00)
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Customer Photos
Features
  • Rich, Throaty Exhaust Tone
  • Loudmouth II "Bullet-Type" Race Mufflers 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
Description
More Power and Sound. This SLP system includes SLP's famous Loudmouth II "Bullet Style" race mufflers for minimal restriction, increased horsepower and an aggressive tone, that are only second to the Loudmouth "shotgun" race resonators for sound.

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 bullet mufflers, the Loud Mouth II system is compatible with all SLP mufflers and resonators including the shotgun style Loud Mouth Resonators 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 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 II 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:
  • (8) exhaust system band clamps
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
  • Mach 1 - 03, 04
  • GT - 99, 00, 01, 02, 03, 04

Fits GT, Mach 1, and Bullitt

Most Helpful Reviews

5/5
Bad to the Bone

I put the Loudmouth ll on along with the SLP long tube headers on my Mach 1 and everyone tells me at's the best sounding exhaust they've heard. I'm glad I use the Loudmouth ll because their loud enoug ...

Read More
Helpful (1)

5/5
Awesome Product!

I've heard this exhaust on a 4v Cobra before and knew I had to have it when I bought my '03 GT. I'm so glad I made the choice to replace the cat back the previous owner put on my car before I bought it. ...

Read More
Helpful (1)

Overall Rating 4.9 out of 5 stars
Read All 68 Reviews

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2 Questions / 6 Answers

Ask a Question

Can this product fit under a v6? I have looked at the dual conversion kits for v6 on here and they aren't true dual conversions as far as I could tell. They use a y pipe..

halo14

  • We offer both dual and true dual conversion kits: dual bolting up to the stock y-pipe and the true dual including an x-pipe with the catback. To answer your question, you can use this SLP Loudmouth System on your V6, but it will require the PaceSetter True Dual Adapter, which is an H-pipe adapter (please see link below). If you're looking for a true dual, x-pipe with catback, we carry a few by Pypes Exhaust: a Catted version, an Off-road version and a Catted with Turndown Tips. If you have any other questions, please don't hesitate to give us a call!

    LisaS

    Good Answer (0) (0)

Show 2 more answers Question Resolved

any body have these with o/r h pipe ? i have lm1s with a mac o/r h pipe and was lookin for a better sound not just loud . how do the lm2s sound ? or whats a better resonator? i like it loud tho

sinko

  • I have these with an off road x-pipe and it sounds great. I had the resonators from the LM1s and it was crazy loud. I'm looking to try the mufflers from the power flo set next

    Ccmustanggt99

    Good Answer (0) (0)

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Customer Reviews (68) Write a Review

Overall Rating 4.9

out of 5 stars

Installation Time:Afternoon

Installation Cost:$100-$250

  • Loudness / Volume 4.384615 4.4
  • Exhaust Note 4.846154 4.8
  • Fit & Finish 4.884615 4.9
  • Bang For Your Buck 4.769231 4.8



  • 5/5

    Installation Time: Afternoon

    February 17, 2014

    GREAT SYSTEM, VERY GOOD QUALITY

    I'VE HAD THIS ON MY 2003 GT SINCE 2008. I HAVE IT IN COMBINATION WITH THE SLP HIGH FLOW CATTED X-PIPE. THE SOUND IS LOUD BUT NOT DEAFENING LOUD LIKE SOME OTHER SYSTEMS. THE EXHAUST NOTE IS VERY THROATY AND SEEMS TO CHANGE AND GET MORE AGGRESSIVE AS THE RPM'S RISE WHICH I LOVE ABOUT IT. IT IS DIFFERENT THAN THE TYPICAL FLOWMASTER SOUND YOU HEAR EVERYWHERE. THE INSTALL WAS EASY BECAUSE THE SYSTEM IS ALL MODULAR WITH MULTIPLE PIECES WHICH ALLOWS YOU TO GET EVERYTHING ALIGNED EXACTLY RIGHT BEFORE YOU TIGHTEN EVERYTHING. ALSO, BECAUSE IT IS A MODULAR SYSTEM IT ALLOWS YOU TO BUY OTHER SLP MUFFLERS AND SWAP THEM OUT QUICKLY AND EASILY. IT IS ALL STAINLESS STEEL SO IT WONT RUST. I HIGHLY RECOMMEND THIS IF YOU ARE LOOKING FOR AN ALTERNATIVE SOUND TO 9 OUT 10 MUSTANGS THAT YOU WILL HEAR ON THE STREET.

    BLOWN03STANG

    Year: 2003 Model: GT Driving Style: Street / Strip 'Stangs I have owned: 3 WARWICK, RI

    Helpful (1) (0)

  • 5/5

    Installation Time: Afternoon

    October 27, 2013

    best exhaust available!

    I bought the slp lm2 a month ago and installed it myself in just a few hours along with the bbk off road x pipe and this is by far the cleanest sounding exhaust. Nice rumble at start up but when u put your foot into the floor it really wakes up. Very aggressive but on the highway cruising its mellow. No drone no headaches. can have a good convo without yelling. I recommend this to everyone

    99blackedoutGT

    Year: 1999 Model: GT Driving Style: Daily Driver 'Stangs I have owned: 1 Lake Grove, NY, USA

    Helpful (1) (0)

  • 5/5

    Installation Time: Afternoon

    October 13, 2013

    Awesome!

    I was split between the LM 1's or LM 2's. My son has the 1's on his 08 GT/CS and it seems a little to much for me. Ordered the 2's and it is perfect sound level for daily driving and opens up when you hit the gas.

    Anaconda67

    Year: 2002 Model: GT Driving Style: Daily Driver 'Stangs I have owned: 4 Pac Northwest

    Helpful (1) (0)

  • 5/5

    Installation Time: Shop Install

    Installation Cost: 0-$100

    August 13, 2013

    Great Product

    Great product! Fitment was perfect! My only complaint is the are not quite as loud as I expected. The sound quality is good but just a bit subtle. I may add an x-pipe at a later date to get more volume out of them. Overall though, I am a happy customer.

    BIGPIMPIN

    Year: 2004 Model: Mach 1 Driving Style: Show 'Stangs I have owned: 2 WV

    Helpful (1) (0)

  • 5/5

    Installation Time: Afternoon

    July 25, 2013

    Sounds good

    I installed the Loudmouth 2 on a 2004 Mach 1 with stock headers and stock mid pipe. Has a real good sound but really quiet unless you are really getting on it. If you are looking for a loud agressive sound, I would plan on changing the mid pipe also. I planned on installing a BBK off road X pipe also but just learned that set up is not legal in my state to pass inspection, so now looking into an X pipe with high flow cats.

    Patrick04

    Year: 2004 Model: Mach 1 Driving Style: Daily Driver 'Stangs I have owned: 2 Virginia Beach, VA, USA

    Helpful (1) (0)

  • 5/5

    Installation Time: Afternoon

    May 08, 2013

    Awesome Product!

    I've heard this exhaust on a 4v Cobra before and knew I had to have it when I bought my '03 GT. I'm so glad I made the choice to replace the cat back the previous owner put on my car before I bought it. Between my long tubes and o/r h pipe and my new SLP LM2, I have the best sounding 2v GT I've ever heard. It has an great deep exhaust note at idle and low throttle and really wakes up and gets loud at full throttle. No annoying drone and you can still have a conversation whil driving.

    Krak3n

    Year: 2003 Model: GT Driving Style: Daily Driver 'Stangs I have owned: 2 Saint Cloud, MN, USA

    Helpful (1) (0)

  • 5/5

    Installation Time: Less than 1 Hour

    April 25, 2013

    Bad to the Bone

    I put the Loudmouth ll on along with the SLP long tube headers on my Mach 1 and everyone tells me at's the best sounding exhaust they've heard. I'm glad I use the Loudmouth ll because their loud enough.

    GOTMACH

    Year: 2004 Model: Mach 1 Driving Style: Show 'Stangs I have owned: 5+ Lapeer, MI, USA

    Helpful (1) (0)

  • 5/5

    Installation Time: Afternoon

    October 28, 2011

    Great sound!

    I have this exhaust on a few of my cars, its the best sounding, loudest exhaust on the market! SLP makes the best tips available as well, so its great looking! Its a no brainer, for the money, you can't beat it.

    TimB

    Year: 2004 Model: Mach 1 Driving Style: Race 'Stangs I have owned: 5+

    Helpful (1) (0)

  • 5/5

    May 21, 2008

    Loudmouth 2

    I just installed this on my 2003 GT. Overall the installation went well. As far as sound goes, it is just what I wanted, a deep tone with a touch of throatiness. I also noticed a gain in performance with my SLP catted x.

    Chad Lang

    Year: 2003 Model: GT

    Helpful (1) (0)

  • 5/5

    February 14, 2008

    Sick Sound

    Just put these on my 2000 GT with the SLP catted X-pipe, amazing sound. Not too loud, but just what I was looking for. Very happy with this choice.

    Justin Murphy

    Year: 2000 Model: GT

    Helpful (1) (0)

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