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

Market Price $539.95 You Save 4% ($22.00)

$517.95

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  • Item 23017
  • MPN# M31007A

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Features & Details

  • 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
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 71 Reviews

Customer Photos (36) Submit Your Photo

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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 (71) Write a Review

Overall Rating 4.9

out of 5 stars

Installation Time:Afternoon

Installation Cost:$100-$250

  • Loudness / Volume 4.413793 4.4
  • Exhaust Note 4.862069 4.9
  • Fit & Finish 4.896552 4.9
  • Bang For Your Buck 4.758621 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 Submodel: GT 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 Submodel: GT 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 Submodel: GT 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 Submodel: Mach 1 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 Submodel: Mach 1 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 Submodel: GT 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 Submodel: Mach 1 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 Submodel: Mach 1

    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 Submodel: 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 Submodel: GT

    Helpful (1) (0)

  • 5/5

    September 27, 2007

    Great Exhaust

    Sounds great and great quality

    01yellowgt

    Helpful (1) (0)

  • 5/5

    March 02, 2010

    Great Muscle Car Sound

    I am completely satisfied with the LM2. It has a nice muscle car sound. It has an aggressive sound while at idle but the pipes really roar when you start shifting through the gears. I would def. recommend this product to everyone!!

    CJ

    Helpful (9) (0)

  • 5/5

    September 04, 2010

    Sounds Amazing

    I had a set of flowmaster super 40's on my Roush 360R before i put these on. I love the way flow's sound but everyone has it, and these SLP's surely made mine sound unique. It has a little bit of a raspy sound but not to where it's annoying or sounds aweful. Im really impressed with the system and i would suggest this to anyone who wants a slighly different exhaust note than every other mustang out there!

    Keith

    Helpful (7) (1)

  • 5/5

    January 19, 2010

    SLP2

    Overall, good sounding exhaust. Has a unique sound of any other cat backing exhaust. I put an off road X-pipe with my SLP2 it sounds very aggresive, and loud with a nice growl.

    Andrew Gallo

    Helpful (7) (1)

  • 5/5

    July 31, 2011

    03 Mach 1

    my dad got this set up for his mach 1, it roars when he starts it to go to work at 4am.. my neighbors say it wakes them up almost every morning! well worth the price

    Branden

    Year: 2003 Submodel: Mach 1

    Helpful (4) (0)

  • 5/5

    Installation Time: Afternoon

    May 10, 2012

    sounds great

    The LM2 doesnt make alot of difference when used with a stock mid pipes and cats I liked it better after i had the slp x pipe installed sounds really good.

    John87

    Year: 2003 Submodel: Mach 1 Aiken, SC, USA

    Helpful (3) (0)

  • 5/5

    Installation Time: Afternoon

    December 11, 2011

    Remarkable

    Installed this exhaust in my driveway in about three hours. The installation was very straight forward and very rewarding. I replaced my flowmaster 40 series mufflers with this kit and the difference is night and day. Starting my car is a treat! Quality is excellent, and of course the slp tips are the best looking ones out there.

    MineralGreyGT

    Year: 2002 Submodel: GT Wilmington, NC

    Helpful (2) (0)

  • 5/5

    April 19, 2009

    Good product

    I\'ve had this exhaust on my stang for over a year now and it has opened up more since I put it on. I am very happy with it. It\'s a clean tone and not raspy and while cruising it doesnt drone. Since I have put a new tb and plenum on the exhaust pops more but not too much. Wouldnt change the exhaust one bit.

    Brian

    Helpful (4) (2)

  • 4/5

    December 16, 2008

    Good choice

    Compared to the sound of the stock exhaust its like night and day. One thing I really like about the exhaust kit was that it idles its fairly quiet until you crack the whip, then people can hear you all across town. For all you dads who are scared your sons will get pulled over like my dad was, you are mistaken. As long as you dont floor it, its legal.

    Ben

    Helpful (1) (0)

  • 5/5

    Installation Time: Afternoon

    June 01, 2012

    LOUD, and Muscle sounding

    MY FAVORITE PART SO FAR. Note: the clips didn't stay tightened all the way and I had my connections spot welded to make sure it stayed all together. This was most likely due to cold but better safe than sorry. When you start the car you really hear your Mustang for the first time. And if your car is still warming up it makes a wonderful kind of pop sound to your exhaust that just sounds mean. Not to mention once you get up in the rpm it just sounds amazing, Looks amazing, Sounds amazing, Just the fitting could be a tad bit better, but not a huge deal very minor.

    01GTSilverPony

    Year: 2001 Submodel: GT Florida, USA

    Helpful (1) (1)

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