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

Market Price $539.95 You Save 4% ($22.00)
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$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
    • GT - 99, 00, 01, 02, 03, 04
    • Mach 1 - 03, 04

    Fits GT, Mach 1, and Bullitt

    People Who Bought This Item Also Bought

    Most Helpful Reviews

    5/5
    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 ...

    Read More
    Helpful (12)

    5/5
    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.

    Helpful (10)

    Overall Rating 4.9 out of 5 stars
    Read All 80 Reviews

    Customer Photos (37) Submit Your Photo

    View All 37 Photos

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    8 Questions / 5 Answers

    Ask a Question

    Will this exhaust fit if have the cats taken off?

    PaulW

    Does anyone know if these pass smog in California w/ catted x pipe?

    Jayzuz2v

    • The SLP Loudmouth II Cat-Back Exhaust will pass CARB however, the Catted X-pipe will not pass CARB.

      Ricky36

    Helpful (0)

    I have pypes violator catback how does this compare in tone, aggression and loudness?

    StevenS

    • Every person will have there own opinion when it comes to exhaust tones and sounds. Generally, the SLP Loudmouth II Cat-Back Exhaust will be slightly quieter than the Pypes Violators however we would recommend listening to some exhaust clips.

      Ricky36

    Helpful (0)

    Would this system bolt up to bbk headers and xpipe?

    MonteG

    • Hey MonteG, This SLP system is able to bolt directly up to he bbk set up and should not run into any issues while beefing the sound of your mustang!

      Cobra_Machine04

    Helpful (0)

    will the lm2 for 99 gt fit my 84 gt can it be made to fit

    Anonymous

    • Hi, This Cat-Back will only fit 99-04 GT, Bullitt, & Mach 1 Mustangs, We do carry the SLP Loudmouth II Mufflers - Pair Item# 23027. Here is the link http://www.americanmuscle.com/slp-loudmouth2-bullet-mufflers.html

      Chris J

    Helpful (0)

    So I like the outside sound of these but I was wondering what's the drone like on the freeway? My friend has the borla ataks w/catted Xpipe and bbk short headers. They sound really nice but after we put on the header and Xpipe they started to drone so bad. I will be daily driving this car and would like a nice sound with as little drone as possible.

    Stewart

    • Well Borla is typically the least likely to Drone and SLP sits on the other end of the spectrum in terms of quality, so you are way more likely to find drone with and SLP. In fact, Borla is one of the few exhaust manufacturers that actually hang their hat on how minimal their drone is relatively.

      JeffAM

    Helpful (0)

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    Customer Reviews (80) Write a Review

    Overall Rating 4.9

    out of 5 stars

    Installation Time:Afternoon

    Installation Cost:$100-$250

    • Loudness / Volume 4.394737 4.4
    • Exhaust Note 4.868421 4.9
    • Fit & Finish 4.894737 4.9
    • Bang For Your Buck 4.736842 4.7



    • 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 (12)

    • 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 (10)

    • 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 (8)

    • 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 (6)

    • 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 (5)

    • 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 (4)

    • 5/5

      Installation Time: Afternoon

      April 04, 2014

      2003 gt with or h pipe

      I had old rusted out flomasters on my gt and decided to go with the loudmouth ll because I heard the 1's were obnoxiously loud especially with no cats. First off I was extremely impressed with the quality of the exhaust and tips. Even the mufflers are polished nice touch. Install took 2 1/2 hours or so start to finish with a lift and one guy working alone. Fairly quiet at idle I would think with stock mid pipe it would be nearly silent so I'm glad I went with no cats. It's not an extremely raw tone in low rpm range similar to glasspacks but the bonus of them not rotting out. In high rpms it SCREAMS. I'm talking wake the neighbors and wake the neighbors at your buddies house across town. I did have one person say it sounded like a Chevy truck but all that's saying is it sounds like a 350. And it it does it sounds like a beefed up 350. Overall good muscle car tone no annoying drone at highway speeds but enough for you to enjoy the noise and at high rpm you better be ready for some serious noise.

      BlaneGress

      Year: 2003 Submodel: GT Indiana, USA

      Helpful (3)

    • 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 (3)

    • 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 (3)

    • 5/5

      November 25, 2007

      European killer

      I recently installed this on my 03 v6, the sound is killer. Many people have said that it sounds like a tuned European car rather than the typically expected ricer tone, I\'m extremely happy and even without the GT bumper it looks great!

      Raul arevalo

      Year: 2003 Submodel: V6

      Helpful (3)

    • 5/5

      Installation Time: Afternoon

      October 01, 2016

      You get what you pay for, great product

      Let my start by saying I have no complaints on this product. And I decided to bite the bullet and buy this catback which wasn't too cheap and I was happy about the money I spent fitment was perfect not one single fitment issue or ground clearance problem this had to be the quickest install ive ever done on my car took just over an hour and not a single leak after putting it all together. Tucked up nice and high. Clears the axle by a mile, and no we're close to my 315's I love it I usually run into problems with any install so this was a nice change of pace and sounds beautiful with an o/r x and mac long tubes!

      93stang772

      Year: 2003 Submodel: GT

      Helpful (2)

    • 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 (2)

    • 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 (2)

    • 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)

    • 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)

    • 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)

    • 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)

    • 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)

    • 5/5

      Installation Time: Afternoon

      March 05, 2013

      Sounds as good as it looks

      I was looking for something slightly different than Flow 40s, of which I had on my 2002 GT for over 200,000 miles. At 240,000 miles I had my engine rebuilt with custom cams, C&L plenum, CAI, LT headers, X pipe, custom chip.... but I kept my tired Flowmasters on. At 250,000 miles, I purchased the SLP Loudmouth IIs. The power increase was significant. The pipes are larger, the tips are beautiful as well as the resonators (not mufflers). These parts were highly polished and look like mirrors. Fit was excellent and removal and install took about 2 hours. Sound is perfect...not too loud until you smash the gas. Sweet!

      Wynnyk

      Year: 2002 Submodel: GT Hughesville, MD, USA

      Helpful (1)

    • 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)

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