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

Market Price $529.95 You Save 3% ($15.00)
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$514.95

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  • Item 23001
  • MPN# M31007

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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

    Review & Installation Video

    Review & Install 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

    CA Residents: Warning: California's Proposition 65

    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
    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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    Customer Photos (82) Submit Your Photo

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    Questions & Answers (45)

    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 (2)

    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 (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.

    Helpful (1) Show 2 more answers

    Will this fit onto a bbk off road x pipe?

    • 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.

    • 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)
    Post Your Question
    10 More Questions
    Hi will this bolt up to a Mac shorty x pipe with Mac LT's? Thanks!! 1 answer
    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
    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
    Will this bolt up to a bbk h pipe? 1 answer
    Will this exhaust pass the emission inspection in California? 1 answer
    Hi, my car won't pass inspection and I'm wondering if it has anything to do w the exhaust even thoug I removed my cat backs so I'm running catless with the lm1 1 answer
    will i need to buy anything else with this to install onto a 2001 gt 1 answer
    I have a stock v6 2002 convertible and I wanted to know if I get this would I have to change my headers and cats to the SLP headers and cats or can this on to the stock v6 headers and cats? 1 answer
    I have a bassani x pipe on my 03 Mach 1 right now. Will this cat back system match up to my x pipe or will I have to change that too? 1 answer
    I have a 04 v6 and I am purchasing this with a v6 mid pipe. Will this cat back clear the stock bumper or will I have to get a gt bumper? 1 answer

    People Who Bought This Item Also Bought

    Customer Reviews (100+) Write a Review

    Overall Rating 4.9

    out of 5 stars

    Installation Time:Afternoon

    Installation Cost:$100-$250

    • Loudness / Volume 4.75419 4.8
    • Exhaust Note 4.815642 4.8
    • Fit & Finish 4.826816 4.8
    • Bang For Your Buck 4.759777 4.8



    • 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 (0)

    • 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 (0)

    • 5/5

      Installation Time: Afternoon

      September 12, 2018

      Surpassed Expectations!!!

      My first car was a black 2000 V6 mustang and all I can remember is visioning the day I would own a GT. 6 years down the road I finally turned that vision into a reality. After finally purchasing my dream car, a stock 2002 Black Mustang GT, it was time for me to begin purchasing all the parts I've added to my wishlist in preparation of this day. After going on Youtube and listening to a variety of exhaust clips I stumbled upon Chris Fix's video where he installed the Slp LM1 and SLP catted x-pipe on his Mustang. THIS WAS THE ONE. Although a bit pricey for someone who is in college it was a must, I ordered it and patiently waited for it to arrive in the mail. After receiving the exhaust I unboxed it... I was in disbelief.. This was going to be the first modification done to my GT. I got the car up in the air, took another look at Chris Fix's installation method and immediately got to work. Keep in mind I only had access to a floor jack, ramps, jack stands, and an abandoned carwash. I installed the cat-back by myself which in turn took me approximately 5 hours to do, with many breaks in between and no rushing, I finally had the last nut tightened down. The start up... I will not forget how excited I was and still am to this day hearing the burble of the exhaust at first start. 2000 rpm is the sweet spot to make a little noise but man at wide open throttle it is unlike anything else. If you're interested in seeing my install hop over to my Youtube channel (PeaceByPiece2V) and watch the install from start to finish to hear a comparison of the stock exhaust vs. the catback. This exhaust will do nothing more than make you smile ear to ear every time you put your foot on the gas.

      SeanL

      Year: 2002 Submodel: GT

      Helpful (1)

    • 5/5

      Installation Time: Afternoon

      September 10, 2018

      Slp catback

      The SLP loudmouth catback sounds amazing on my 2003 gt. I highly recommend this set up for someone doesn’t want to spend the money on an 800 dollar exhaust. Over all it only took a little over an hour to install which was fairly easy. As much as I love the 3.5 inch exhaust tips, I do wish they were capable to stick out past the bumper a bit further. Over all I am very pleased!

      BryceH

      Year: 2003 Submodel: GT

      Helpful (0)

    • 5/5

      Installation Time: Shop Install

      Installation Cost: $250-$500

      August 29, 2018

      SLP Loudmouth

      Wow! Really diggin the sound this exhaust makes. I'd rather listen to it than my stereo. The guys at AM are very helpful. Appreciate all of you. Will definitely continue to Mod my Mustang, with AM staff guidance. Thank you

      RommelK

      Year: 2001 Submodel: GT

      Helpful (0)

    • 5/5

      Installation Time: Less than 1 Hour

      August 28, 2018

      Slp loudmouth cat-back

      This exhaust system is freakin awesome!!!! Gives my pony a unique throaty sound that is just out of this world!!! Not to loud when just cruising but man-o-man when you hammer down on it does it come alive and to note, it's not a annoying loud but it's loud enough to turns heads!! Thanks A.M.

      ChadB

      Year: 2004 Submodel: GT

      Helpful (0)

    • 5/5

      Installation Time: Afternoon

      August 13, 2018

      Very impressed

      Not the simplest to install if u don’t have a lift but that’s with anything but patience and attention to detail is well worth it... it is loud and aggressive and a real head turner... I’ve gotten so many compliments in just a short time... well with the money

      Gavin

      Year: 2000 Submodel: GT

      Helpful (1)

    • 5/5

      Installation Time: Shop Install

      Installation Cost: 0-$100

      August 08, 2018

      Lm1 off the chain

      These LM1 are just what I was looking for boy do they make my mustang come alive it's very lound going threw the gears boy o boy man o man never go back to flowmaster

      GregoryG

      Year: 2003 Submodel: GT

      Helpful (1)

    • 5/5

      Installation Time: Afternoon

      July 30, 2018

      Slp loudmouth

      Great product sounds amazing with stock cats and hpipe

      TrevorK

      Year: 2001 Submodel: GT

      Helpful (1)

    • 5/5

      Installation Time: Afternoon

      July 15, 2018

      2004 GT

      You cannot find another Cat-Back exhaust system for this car for the price and performance. Very pleased with everything and installation was quick and easy. Although, to get the full sound effect of this system, a midpipe is almost necessary.

      ColeM

      Year: 2004 Submodel: GT

      Helpful (2)

    • 5/5

      Installation Time: Afternoon

      June 25, 2018

      Sound real nice

      Glad I went with these because they sound mean, very easy install!

      DavidI

      Year: 2000 Submodel: GT

      Helpful (1)

    • 5/5

      Installation Time: Less than 1 Hour

      June 04, 2018

      Awesome Exhaust

      It was easy to install, it sounds amazing at idle and went you get on it everyone turns there heads to see what's going on. I recommend anyone to make there mustang louder to get this product

      LucasH

      Year: 2001 Submodel: GT

      Helpful (3)

    • 5/5

      Installation Time: Afternoon

      May 31, 2018

      Sounds AMAZING

      Sounds really good if you like loud! I’ve had many compliments. Everyone says it sounds like a 4v and not a 2v. Unique great sounding exhaust

      DevanK

      Year: 2002 Submodel: GT

      Helpful (3)

    • 5/5

      Installation Time: Less than 1 Hour

      May 30, 2018

      Mean

      These cat back are amazing they really wake up your car. I had no trouble installing what so ever. Super easy. It took under an hour and I did it at home with no life just a drive on ramps.

      NathanE

      Year: 2003 Submodel: GT

      Helpful (3)

    • 5/5

      Installation Time: Afternoon

      May 28, 2018

      awesome

      very happy with the end result great product would recommend buying.

      GaryE

      Year: 2003 Submodel: GT

      Helpful (2)

    • 5/5

      Installation Time: Afternoon

      May 22, 2018

      Great Product.

      Worth every penny. Only took a few hrs to install and all parts fit perfectly.

      DerrickH

      Year: 2003 Submodel: GT

      Helpful (3)

    • 5/5

      Installation Time: Afternoon

      May 22, 2018

      Slp loudmouth

      I am very pleased with this exhaust,it has a rich throaty sound and that's what I was looking for! I couldn't be happier!

      Gmanrocks

      Year: 2004 Submodel: GT

      Helpful (3)

    • 1/5

      May 21, 2018

      Defected part!

      Everything was great until the driver side went on. The tailpipe end that connects to the over axle pipe were the same diameter. The tailpipe end should of been wider but it wasn't and the bracket for the muffler broke..So I had to spend $200 to get the pipes welded...Highly disappointed and I talked with an americanmuscle rep and they wanted me to ship the whole exhaust back and get a new one or order a new one take the one piece out and send it back for a refund...which makes no sense at all..I was not going to have my car down for 2-4 weeks as I am working overseas....

      edwardd

      Year: 2004 Submodel: GT

      Helpful (4)

    • 4/5

      Installation Time: Less than 1 Hour

      May 15, 2018

      SLP loudmouth

      Fit was great easy also and was quick to put on.The sound is amazing good for your money best purchase

      RobertS

      Year: 2004 Submodel: Mach 1

      Helpful (3)

    • 5/5

      Installation Time: Afternoon

      May 15, 2018

      Very nice system

      The product has a very clean look and a nice rumble at 2k rpm but if you want it to be loud would highly suggest getting a X pipe.

      BrendenD

      Year: 2004 Submodel: GT

      Helpful (3)

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