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Magnaflow Street Series Cat-Back Exhaust (99-04 GT, Mach 1)

Item 48012
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      Review & Installation Video

      Hey I’m Justin with, and this is my quick look into the Magnaflow catback exhaust system fitting the 99-04 Mustang GT and Mach 1. Right off the bat, I can tell you this isn’t going to be the loudest kit in the world, thanks in part to the traditional chambered muffler design. What you can expect from this kit is for it to be slightly more aggressive than stock, when idle and while cruising, but really comes to life when you get on the throttle. Just because this system is a little on the quiet side doesn’t make it a bad exhaust, as a matter of fact it’s far from it. We’re looking at a full stainless steel constructions throughout, including 2.5” mandrel bent tubing, quality welds, and a quality finish, both on those chambered mufflers, and on those 3.5” flared polished tips. As the factory exhaust is all one piece you will need to cut it off with a saw or something similar, once you get that out of the way, getting the magnaflow installed is a very straightforward task, that should take you about 2 hours using standard hand tools. Now let’s hear how Magnaflow’s catback exhaust system sounds compared to your factory exhaust.

      Product Information

      Features, Description, Reviews, Q&A, Specs & Installation


      • Classic Muscle Car Sound
      • Street Series Muffler - Straight-Through Design
      • Durable, Stainless Steel Construction
      • 2.5" Mandrel-Bent Tubing
      • 3.5" Polished Stainless Steel Tips
      • Fits 1999-2004 GT, Bullitt and Mach 1 Mustangs


      Free Flowing Exhaust. Magnaflow delivers the ultimate exhaust for the 99-04 GT, Bullitt, and Mach 1 Mustangs with this Street Cat-Back Exhaust System. By reducing back pressure for a free flowing exhaust, more power and torque is produced where it belongs - at the rear wheels.

      Classic Muscle Car Sound. The Magnaflow Cat-Back Exhaust System includes a set of two Street Series Mufflers that feature a free-flowing, straight-through perforated stainless steel core, with stainless mesh wrap and acoustical fiber fill to deliver that smooth, deep muscle car tone.

      Quality Construction. Each piece of this Street Exhaust is made from 2.5" mandrel bent stainless steel tubing for long life and a perfect fit. The system is finished off with brightly polished 3.5" stainless steel tips that exit from the stock location for impressive good looks.

      Application. Made to be a direct bolt on, this Magnaflow Street Cat-Back Exhaust will bolt straight up to the factory Mid Pipe without any extra modifications required on 1999-2004 GT, 2001 Bullitt or 2003-2004 Mach 1 Mustangs.

      Note: Coupon codes cannot be applied to this product.

      Lifetime Warranty is included with all Magnaflow catback systems.

      Fitment: 1999 2000 2001 2002 2003 2004 Details

      MPN# 15671

      CA Residents: WARNING: Cancer and Reproductive Harm -


      Customer Reviews (40)

      Write a Review

      Ratings Summary

      4.7 out of 5 overall rating from 40 customers

      Installation Time: Full Day

      Installation Cost: $100-$250

      • April 08, 2019

        5 1999 GT - mustanglvr99 Installation Time: Shop Install

        Practical, easy to install, will buy it again

        excellent product, easy installation, love the way it looks and sounds, I am satisfied with my purchase

        Helpful (0)
      • February 05, 2019

        3 2003 GT - KennethC Installation Time: Afternoon

        Nice sounding exhaust

        Exhaust sounds great. What a nice deep tone without being overly loud. The band clamps don’t hold good at all. I’ve been trying to turn and twist the left tailpipe to stop it from the contact with the rear sway bar every time I go over the smallest crack or bump in the road. The rattle is frustrating. I’ve tried a half dozen times to fix this and the tailpipe is showing scratches and rub marks and I’m kind of lost about what to do. The only thing l can try is denting the pipe in to allow for clearance. Either I dent it in or the sway bar will wear a hole in it. They really should have made a little flat area in this area. Once this rattle is fixed I’m going to tac weld them so they don’t loosen again.

        Helpful (2)
      • November 19, 2018

        4 2004 GT - AntonioS Installation Time: Afternoon

        Great at wot

        Sounds great when you get on it and can be heard from down the street. clamps didn't hold very well and i decided to take the axle-backs off and it sounds deeper and throatier with dumps off the muffler. also don't have cats so the sound is better.

        Helpful (3)
      • October 14, 2017

        4 2004 GT - JoeP Installation Time: Shop Install Installation Cost: $100-$250

        Deep Tone

        System is a little deeper than stock at idle, but gets louder when you get on the throttle. Slight drone from 1,700 - 2,100 rpms but quickly goes away. Great construction quality.

        Helpful (11)
      • September 05, 2017

        5 2003 GT - paule Installation Time: Afternoon

        Sounds good

        Installed on my 2003 Mustang GT sounds good nice-looking pipes but the driver side was kind of tricky kind of tight in that area but overall good product would recommend

        Helpful (9)
      • September 05, 2017

        5 2003 GT - paul Installation Time: Afternoon

        Sounds good

        Installed on my 2003 Mustang GT sounds good nice-looking pipes but the driver side was kind of tricky kind of tight in that area but overall good product would recommend

        Helpful (6)
      • August 15, 2017

        5 2004 GT - Applehead Installation Time: Afternoon

        Magnaflow catback for the win!!!

        I was tired of the flowmaster drone, with 410s on the interstate the interior resonance was horrible. With this catback I no longer have that annoying drone and it still sounds killer!!! Throttle response is better and you can definitely feel the difference with these straight through mufflers!!! I recommend this to anyone looking to get rid of that dredged flowmaster drone, and make a little more power also!!

        Helpful (6)
      • April 06, 2017

        4 2001 GT - PedroH Installation Time: Afternoon

        Perfect sound.

        Sounds great, fits perfectly. Only issue I ran into where the clamps, for whatever reason they didn't hold, so I purchased some wider ones from advance auto and that took care of the constant re tightening. Will buy these for my next project. Not obnoxiously loud during cruising, but at wot... The sound will wake up the dead! Sound is deep, not tinny.

        Helpful (6)
      • January 26, 2016

        5 2000 GT - don123 Installation Time: Afternoon

        Awesome sound and quality

        I bought the magnaflows to replace my old flowmasters. Installation was a breeze! No more drone! Quiet when at idle but when you get on it, it sounds great!

        Helpful (11)
      • February 24, 2015

        5 1999 GT - GTsmiles Installation Time: Shop Install Installation Cost: $100-$250

        Magnaflow Catback Long Term Performance

        No rust or discoloration anywhere on the entire system after 8 years of use so you know this system will last. I like the etched tips that I can only get from Magnaflow. They replaced one of mine that got damaged as long I as provided proof of purchase so they don’t just sell them to anyone. Also you can swivel the hanger to center the tip before final install so it looks right. Get compliments, not complaints, from the neighbors using it with FFRP shorty headers and Bassani x-pipe. No drone and really quiet in the car above 2500 rpm on the highway which makes this system a keeper.

        Helpful (10)

      Questions & Answers (8 answers)

      5 Top Rated Questions

      Will this Cat-Back Exhaust and the Magnaflow Direct-Fit California Catted X-Pipe work together in my 01 Gt Convertible?

      • These will work together yes.

      Helpful (0)

      Is this street legal in California will emissions test pass?

      • The Magnaflow Street Cat-Back Exhaust (99-04 GT, Mach 1) will not affect emissions however it will be louder than stock. We recommend consulting local laws as to legality in your area.

      Helpful (0)

      How load does it measure in decibels? Is it around 72 decibels under 35 MPH.

      • At this time we do not have decibel ratings for any of our exhausts.

      Helpful (0)

      would this gt catback fit on a v6 if you removed the stock y midpipe and ran a h pipe with long tube headers?

      • This will certainly fit if you purchase the MAC Off-road H-pipe that works with long tube headers we offer. I will post a link to this product below:

      Helpful (0)

      Hi, roughly what kind of hp/torque can I get from bbk headers, magnaflow street catbacks and flowmaster catted h-pipes ? Standard is 260/302. Thanks, Frank

      • Power gains will be different for each setup, for example; if you have BBK Ceramic Tuned Length Shorty Headers (96-04 GT) item #56101 ( with Magnaflow Street Catbacks and Flowmaster Catted H-Pipes you can gain around 15HP. If you have BBK Ceramic Long Tube Headers - Manual (96-04 GT) item #56010 ( with a tune you could see 25-30HP.

      Helpful (0)
      Post Your Question
      3 More Questions
      Will this system fit my 99 SVT Cobra Mustang? 1 answer
      Will this work with the sn95? Would this exhaust system fit the sn95? Can I just only modify the hangers so this setup can fit? 1 answer
      Magnaflow catback exhaust installation? The actual color of my 2004 GT is Merlot Clearcoat, but that option was not listed. My question is: do you need any type of heat shield between the mufflers and the floor pans to keep the inside floors from becoming too hot? The original factory mufflers had heat shields attached to the top of them. 2 answers

      Installation & What's in the Box

      Installation Info

      What's in the Box

      • (2) Flow Tubes
      • (2) Tail Pipes
      • (2) Mufflers
      • (2) Turn-Down Tips
      • (2) Set Screws w/ Allen Wrench
      • (2) Tip Hangers
      • (6) 1.25" x 2.5" Band Clamps
      • (2) Header Mounting Flanges

      Tech Specs

      Cat-Back Exhaust Specifications
      Piping Material:Stainless Steel Tip Material :Polished Stainless Steel
      Piping Size:2.5"Tip Size:3.5"
      Muffler Type:Straight-throughFitment:1999-2004 GT / Mach 1 / Bullitt

      Will It Fit My Mustang

      • Bullitt - 01
      • GT - 99, 00, 01, 02, 03, 04
      • Mach 1 - 03, 04

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