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

Market Price $561.95 You Save 4% ($22.00)
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$539.95

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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?

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    9 Questions / 13 Answers

    Ask a Question

    What makes this model different the the first version? Thanks.

    Mustangman

    • The difference between this exhaust and the first version would be the muffler style. This exhaust would have a bullet style muffler rather than the shotgun resonators that the first loudmouth exhaust has. This exhaust would be louder as well as have a deeper throatier tone to it when compared to the first loudmouth exhaust.

      AMJalisaB

    Helpful (0)

    Will this exhaust fit if have the cats taken off?

    PaulW

    • The SLP Loudmouth II Cat-Back Exhaust will work with an off road mid-pipe. If you have any other questions or concerns feel free to call or chat in.

      Pat K

    Helpful (0)

    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)

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    Customer Reviews (86) Write a Review

    Overall Rating 4.9

    out of 5 stars

    Installation Time:Afternoon

    Installation Cost:$100-$250

    • Loudness / Volume 4.295455 4.3
    • Exhaust Note 4.886364 4.9
    • Fit & Finish 4.909091 4.9
    • Bang For Your Buck 4.704545 4.7



    • 5/5

      Installation Time: Afternoon

      June 09, 2018

      Great exhaust, read this for torque specs

      This system was easy to install, although if you have access to a lift I highly reccomand you use it. I used ramps, and I could have saved myself a lot of time if I had access to a lift. Really lube the hangers before you try to wrestle them off or just remove the 2 bolts and pull the hanger down, but you’ll still need to lube the hangers to really easily get them off. I found it easier to just remove the hangers and do it standing up rather than on my back under the car. I had to call SLP for torque specs on the band clamps and even the guy I spoke with had to call me back later because he wasn’t sure. 25-30 lbs of torque is what the torque should be on the band clamps. I knew I was going to add an X-pipe at some point, so I went with the LM 2, but if I wasn’t, I would have gone with the LM1. This system is much improved over stock, is much deeper, and has a great growl to it, but doesn’t have much more volume to it over stock which is great if you’re looking for a quiet exhaust. Once I add an X-pipe to it, it will be a little bit louder for sure. I certainly don’t want an offensively loud exhaust, but this one is very quiet even for me just as a catback alone.

      TroyC

      Year: 2004 Submodel: GT

      Helpful (0)

    • 5/5

      Installation Time: Afternoon

      April 29, 2018

      Really nice cat system

      Quality cat system that has great tone. Not obnoxiously loud and looks great installed.

      StephenY

      Year: 2003 Submodel: Mach 1

      Helpful (1)

    • 5/5

      Installation Time: Afternoon

      April 25, 2018

      Best exhaust on the market

      The exhaust is by far the best on the market! I was running a magnaflow catback system and wanted something different. The install was super easy, I did it in my garage in about 2 hours! Everything lined up well and fit perfectly! Not one thing bad to say! The sound was the best part, being paired with an O/R h pipe; it rumbles at idle and sounds amazing throughout the RPM range! Highly recommend, and thanks again American Muscle!

      MattM

      Year: 2002 Submodel: GT

      Helpful (1)

    • 5/5

      March 26, 2018

      Nice system

      I bought this system for my '99 GT convertible and was a little worried about it being to loud with the top down. I will say this system sounds great and is not overly loud has a nice throaty sound. I installed the system at my shop and took my time just over an hour or so. Very straight forward bolt up. If you are looking for a nice sound but not extremely loud this is the right system even great in a convertible. Great purchase very satisfied!

      ChuckA

      Year: 1999 Submodel: GT

      Helpful (1)

    • 5/5

      Installation Time: Less than 1 Hour

      March 07, 2018

      Sounds great and throaty

      I have no cats and at one point no muffler either, the car was too loud so i looked around for a aggressive exhaust that will also muffle the sound some but stay loud and good sounding. So i landed on this and it sounds great after about a week the exhaust broke in and sounded great!!. Would definitely recommend for cars with no cats. If you have cats i think it will be too quiet. Btw i had a lift for my install.

      DarrenF

      Year: 2000 Submodel: GT

      Helpful (1)

    • 5/5

      Installation Time: Shop Install

      February 02, 2018

      Nice!

      Paired this up with an x pipe and they sound great! I would definitely recommend this cat back!

      KevinE

      Year: 2001 Submodel: GT

      Helpful (1)

    • 5/5

      Installation Time: Afternoon

      December 18, 2017

      Nice system

      Easy to install. Toughest part is removing the old system---do not spare the Liquid Wrench (or similar) and put that new metal blade you've been saving in your reciprocating saw. Took my time, did it in my garage with the car on jackstands...probably took 4hrs not counting coffee, snacks, restroom, and a nap (hey, I'm over 60...you kids should be able to knock this out easy and still make the evening cruise). Louder inside the car than stock, but not debilitating...drones a bit right at 2000rpm in 4th, but modulates with minor speed adjustment. Outside the car, noise at idle only marginally above the old clapped out stockers (which is the way I wanted it). Subjectively, the car seems to breathe better.

      Kim

      Year: 2000 Submodel: GT

      Helpful (2)

    • 5/5

      Installation Time: Afternoon

      October 02, 2017

      Loudmouth 2

      Great look,sound and fit.!Had flowmaster 40's but wanted to change up didn't go wrong gave my car a deep rumble and and look.

      Jeremy

      Year: 2003 Submodel: GT

      Helpful (2)

    • 5/5

      Installation Time: Less than 1 Hour

      September 29, 2017

      Not as loud as descried

      Fits perfectly. The reviews on the web made it seem like this was a raspy system, it is not. Loud rumble under full throttle. City driving, its respectable but loud enough to turn heads.

      Fabio

      Year: 2003 Submodel: Mach 1

      Helpful (1)

    • 5/5

      Installation Time: Less than 1 Hour

      September 21, 2017

      Great! Not loud like LM1s

      These are not as loud as LM1s and have a clean, low rumble. It is quite at crusing speeds and loud at WOT. I've had Borla Stingers on my other Mach 1 and wanted to switch it up. The tips are the best on the market for looks, fit was perfect, and sounds great. Perfect for somebody that wants that old fashioned clean rumble. Does sound a lot different on 4Vs compared to 2Vs.

      ChristianH

      Year: 2003 Submodel: Mach 1

      Helpful (1)

    • 5/5

      Installation Time: Afternoon

      August 30, 2017

      loudmouth

      the exhaust sounds amazing looks good to was not bad to put in .the hard part was cutting out the old one

      MarkS

      Year: 2003 Submodel: GT

      Helpful (2)

    • 5/5

      Installation Time: Afternoon

      August 19, 2017

      Best sounding Exhaust

      if you are looking for the perfect mix between high quality sound and volume, this is the exhaust for you. The instilation took me a long time but hust because i wasnt working in optimal working conditions and the stock exhaust was a nightmare to get off, but in terms of the SLP install, it took probably about an hour and a half. Im blown away, none of the videos or sound clips do it justice, in person it sounds absolutely amazing, even on the stock H pipe!

      PaulD

      Year: 2002 Submodel: GT

      Helpful (2)

    • 5/5

      Installation Time: Afternoon

      June 01, 2017

      SLP Loudmouth 2

      This exhaust is very throaty paired up with my BBK Xpipe...like music to my ears every time I start it up...If you are thinking about getting a catback this is the one to get!! Thanks AM!!!

      BrandonF

      Year: 2004 Submodel: GT

      Helpful (1)

    • 4/5

      January 07, 2017

      SLP LM2 Cat-Back

      First of all I bought this as it uses stainless steel piping. Install was very easy, rather quick in my opinion. I would not be afraid to recommend encouraging beginners to do this install. I noticed very minimal performance gains by the seat of the pants. The sound is exactly what I was looking for. Has a deep throaty sound that is not extremely loud and almost docile at low rpms. When you get in the throttle it really wakes up and sounds great.

      DC

      Year: 2003 Submodel: GT

      Helpful (2)

    • 5/5

      Installation Time: Less than 1 Hour

      December 10, 2016

      LMII Catback

      I have a 2001 Bullitt with panhard bar. I wanted an exhaust that would not require custom work. The LMII fit perfect and sounds awesome. Idles louder than stock and deeper, and sounds really good through the RPMs. No drone at all. I think I will get the LMI for the track days !

      Ncst8man1999

      Year: 2001 Submodel: Bullitt

      Helpful (1)

    • 5/5

      Installation Time: Less than 1 Hour

      November 30, 2016

      Loudmouth

      2nd one I have had one on my 04 mach one just bought a 03 mach one this was the first upgrade of many comfortable sound till you hit the gas SOUNDS awesome

      skeeterspopa

      Year: 2003 Submodel: Mach 1

      Helpful (2)

    • 5/5

      Installation Time: Afternoon

      October 24, 2016

      Aggressive

      With an x pipe this exhaust is very unique sounding . Very aggressive, loud when u smash on it, but nice at idle . I don't know how it sound with the factory h pipe , but with an un catted o/r x pipe it sounds amazing

      Alo1889

      Year: 2004 Submodel: GT

      Helpful (1)

    • 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 (3)

    • 5/5

      Installation Time: Afternoon

      May 19, 2016

      Boom chaka-laka!

      I've been wanting to upgrade the pipes on my Roush 360R for years. I finally ran out of excuses not to and pulled the trigger on SLPs. It's hard, deciding between so many cat back options. You look at the price, you examine the exhaust tips, you listen to audio clips on YouTube. In the end you end up deciding on some combo of those factors. I can tell you I don't regret the decision at all. The cans are beautiful to look at, too bad no one will ever see them. Nice growl when you're into the throttle, little to no drone cruising at highway speeds, and some nice crackle lifting off the throttle. I did these in my garage on jack stands, I'd definitely recommend a lift. It was a pain trying to adjust, hold and wrench all while practically lying upside down. I'm already looking at X-pipes as next spring's upgrade.

      Ken

      Year: 2002 Submodel: Other

      Helpful (2)

    • 5/5

      Installation Time: Afternoon

      March 01, 2016

      Sounds awesome.

      I researched for a week. Finally decided on the lm2. As far as fitment. Pretty good. Slight modding needed. Haha no big deal. Take your time. Cruising it's pretty smooth and slight growl. Heavy foot loud. And wot sounds like the world coming to an end. I have a pair of lm1s already and am gonna install and see difference. But as far as drone. There is none. If you've had flow masters. These will sound like a quiet nights sleep. Oh and I have this paired with pypes off-road h pipe.

      hubaduba12

      Year: 1999 Submodel: GT

      Helpful (1)

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