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Flowpack Aluminized Cat-to-Axle H-Pipe Kit (11-14 GT)

AmericanMuscle no longer carries the Flowpack Aluminized Cat-to-Axle H-Pipe Kit (11-14 GT). Please check out 2010-2014 Mustang H-Pipes for an updated selection.

Features & Details

  • Improves Exhaust Flow for More Power
  • Muscle Car Rumble
  • Mid Muffler Design
  • Aluminized Steel Construction
  • Clamp-On Design
  • Reuses Stock Catalytic Converters
  • Uses O.E. or Aftermarket Axle-Back
  • Fits 2011-2014 GT Mustangs
Better Flow, More Power. Ford actually did a decent job on the Mustangs catalytic converters, but the stock factor piping can be restrictive. That's where the Heartthrob Flowpack Cat-to-Axle X-Pipe Kit comes into play. Featuring a H crossover and 3" free-flowing mandrel-bent piping, this Heartthrob Mid Pipe will dramatically improve exhaust flow for more power and sound that you can feel.

Muscle Car Rumble. This free flowing Heartthrob Flowpack Cat-to-Axle H-Pipe Kit for the 2011-2013+ GT Mustang's not only increases power, but it also adds a deep muscle car rumble to the sound of your exhaust with its classic "H" crossover pipe and mid muffler design.

Reuses Stock Cats. The installation of the Heartthrob Exhaust cat to axle system requires removing the stock exhaust piping from the catalytic converters back to the axle-back, and reuses the factory catalytic converters saving you money. Clamps and instructions are provided.

Versatile Design. The unique design of the Heartthrob Cat-to-Axle exhaust kit allows you to install the axle-back of your choice. You can keep the stock mufflers for a mild sound or go with a set of muffler deletes for a wild sound. The choice is up to you.

Durable Construction. Heartthrob uses free-flowing 3" diameter CNC mandrel bent aluminized tubing with a H style crossover and high flow straight-thru Flowpack mufflers to improve exhaust flow to provide a significant increase in power and sound.

Application. This Heartthrob Flowpack H-Pipe Kit is designed to fit the 2011-2014 GT Mustangs with either the stock exhaust manifolds or aftermarket shorty style headers installed.

Fitment: Details

CA Residents: WARNING: Cancer and Reproductive Harm -

What's in the Box
  • (1) H-pipe
  • (2) Mufflers
  • (2) Over axle pipes
Installation Info
Tech Specs
Mid Pipe Specifications
Style Mid Pipe: "H" Type Headers Required: Shorty or Stock Manifolds
Piping Material: Aluminized Steel Piping Size: 3"
Catalytic Converter: Reuses stock Catalytic Converters Fitment: 2011-2014 GT Mustangs
Will it fit my Mustang?

    Customer Photos

      Questions & Answers (4)

      4 Top Rated Questions

      Does this work/sound well with Borla S-Type Axlebacks? Would this H-Pipe fit properly to the Borla S-Types I have on the car? I'm hoping that it will also add a deeper/louder sound compared to the stock H-Pipe I have on the car. Also should I send this change in to AM to have them alter my 93 Bama Race tune or is the change not worth a modification?

      • Yes. It does take patience fitting the over the axle section but can be done. As to the tune, if you already have a current 93 octane tune you should be fine. I have a 2012 GT and with the Heartthrob H pipe and Heartthrob axlebacks saw 30 additional RWHP and I have stock tune from Ford. It will sound nice with the Borla's as it is a deeper sound using the bigger H pipe. More dramatic sound is using the Heartthob axlebacks as well but they may tend to drone at 2K RPM at cruising speeds.

      Helpful (1)

      is this Heartthrob Cat - Axle kit true 3" at the rear muffler connector? Or does it neck down to 2.75" or worse, down to 2.5" like so many others?

      • The Heartthrob Flowpack Cat-to-Axle H-Pipe Kit has to step down to 2.5" to pair up with the factory or aftermarket mufflers. If you are looking for a true 3" exhaust with absolutely no step downs in it you will have to have one fabricated for your car.

      Helpful (0)

      Roush Axle-back Fitment? I'm looking to get a mid pipe but since these are 3" piping how would it affect axle backs like roush with 2.75"?

      • Some minor modification will be required to match the Roush output points. Their exhaust tips are at a slightly wider stance.

      Helpful (0)

      Will this work with the RTR axlebacks? I have the RTR axlebacks currently installed, and am still wanting a little more volume to my exhaust, especially in the higher RPMS. Will this work with said mufflers? As i understand, this is a midpipe that bolts up to the OEM cats. So i shouldn't have any problem with this, correct? Will this require a tune? Thanks!

      • Yes, you can use either the factory axle-back or an aftermarket axle-back along with this Flowpack H-pipe Kit. The RTR Axle-back will bolt up just fine as they have the same 3" piping diameter. This combination would not require a new custom tune. Bolt up and enjoy!!

      Helpful (0)
      Post Your Question

        Customer Reviews (9) Write a Review

        Overall Rating 3.6

        out of 5 stars

        Installation Time:Weekend

        Installation Cost:$250-$500

        • Loudness / Volume 3.444444 3.4
        • Exhaust Note 4.555555 4.6
        • Fit & Finish 2.444444 2.4
        • Bang For Your Buck 3.777778 3.8

        • 1/5

          Installation Time: Shop Install

          Installation Cost: 0-$100

          September 20, 2016

          Do not buy

          Do not buy this exhaust as it will not fit a coyote mustang without major modification. Took it to a muffler shop and they spent an hour trying to get it fit with no luck. Luckily American muscle was great and accepted the return. I called and they give me no hesitation to return the exhaust. For this reason I bought my replacement exhaust with AM.


          Year: 2013 Submodel: GT

          Helpful (7)

        • 3/5

          Installation Time: Shop Install

          Installation Cost: $100-$250

          November 22, 2014

          You can do better.

          The piping on the drivers side did not fit properly clear the differential on the car. It hit would bang against it on road dips. After i took it back to the shop; i had to pay extra to have the mechanic do some cutting and splicing with welds to shorten the pipe enough to clear it. I don't know why one side worked and the other didn't. The Flowpacks cut the volume down and completly eliminate any rasp. So there is a give and take there . definitely can notice the power increase which is great. If you want a big sound difference I would probably get something with either no resonators or shorter resonators.


          Year: 2014 Submodel: GT Los Angeles, CA, USA

          Helpful (7)

        • 4/5

          Installation Time: Afternoon

          April 03, 2014


          The pipe wasn't the easiest thing to install. It didn't fit my Magnaflow axelbacks because of the rounded ends. However, after some cutting and clamping, it turned out pretty good. Only put about 100 miles on it then my engine blew with 27k miles. NOT the pipe's fault, just one of the lemons I guess. But from what I heard in the short time I had it installed it sounds great. Not too loud but defiantly cleared up the higher RPM sound into more of a rumble. I would recommend this product if your not looking for an obnoxiously loud sound.


          Year: 2012 Submodel: GT Pittsburgh, PA

          Helpful (8)

        • 3/5

          Installation Time: Afternoon

          June 24, 2013

          Best bang for buck

          I read all the reviews before ordering the kit. I was prepared to do some custom fitting and installed it at a shop with a lift. It was pretty frustrating but worked much better once I chopped off about an inch and a half off of the mid section. As of now the tail pipes are still not lined up. I already have the Flowmaster Hushpower axle-back. With the Hearthrob flowpacks it almost seems quieter in the car with no drone at all. Which in my opinion is good. As far as the claim with horsepower numbers? I'm not quite sure but when I open it up at a higher rpm it seems to pull a little harder. No track times with the new exhaust yet.


          Year: 2011 Submodel: GT Newmarket, England

          Helpful (7)

        • 5/5

          Installation Time: Full Day

          June 13, 2013


          As described by Heartthrob they give a nice deep tone. It sounds like my fox body 5.0! It sucks putting them on in the driveway, you will need to cut stock exhaust over axle portion to remove. I have stock manifold, SLP high flow cats, and flowmaster hushpower mufflers. It sounds deep at lower RPMs and will open up when you step on it. They claim 25hp gains but I have 600rwhp so it is a little hard to notice a difference. I previously had hushpower and cat delete exhaust mods only. I couldn't drive around with the windows down, it was so loud! Now I love cruising with windows down. You may want to degrease the entire kit, if not it will take forever for the pipes to burn off grease. I ended up installing from mufflers to the cats instead of what the direction said. This may have work better for since it was a driveway install.


          Year: 2013 Submodel: GT Butler, PA

          Helpful (6)

        • 4/5

          Installation Time: Shop Install

          Installation Cost: $1000+

          April 21, 2013

          Great exhaust note!

          This kit was as advertised. The quality is good and the exhaust note is great. There is no room for error when doing the install. The over the axle pipes are very close to the floor and rear end housing. 3 inch exhausts are challenging on street cars. My car has a sport suspension from a major manufacture and the rear is 1.5" lower than stock. That also has something to do with the tight fit I believe. For a stock suspension it will be a little more forgiving. As with all modifications there is always a chance to mess up NVH the factory has tried so hard to make as good as possible. The quality and performance of this product is good overall.


          Year: 2012 Submodel: GT Augusta, ME, USA

          Helpful (7)

        • 4/5

          Installation Time: Afternoon

          March 19, 2013


          Installed the h-pipe after driving with just Roush axle backs for 1 year. Did not have to cut any length of pipe. Exhaust sound is a lot lower of a tone. Not as raspy as the stock h. Install on drive way. Had to cut old intermediate pipe out. Was able to use lift to get the final adjustments set. Still smell oil coating burning off after 2 1/2 weeks.


          Year: 2012 Submodel: GT Rio Rancho, NM

          Helpful (6)

        • 4/5

          Installation Time: Full Day

          September 06, 2012

          Great sound, terrible fitment.

          This exhaust sounds great with the roush axle-backs. I was debating whether I should go with this kit with the flowpacks, or go staight-pipe. This kit with the flowpacks is perfect! It is deeper and a slight bit louder, also not as raspy. Now for the bad. Heartthrob still has not fixed their fitment issues. It took me an estimated 10 hours to install this with floors jacks, but I also installed a set of JBA High-flow cats. I had to cut off 2" from the h-pipe in order for everything to fit together. Even so, I can still here one of the pipes rubbing in the back over the axle. It is a pain to take off the oem pipes if you only have jack stands. You will end up having to take off the shock and sway bar in order to get the springs out to afford you the extra room to remove them. i would HIGHLY recommend a shop lift. It would have cut my time by probably 75%. All in all, it is a good exhaust for the price. I would say Heartthrobs statement of 16HP is pretty accurate. I felt like the car had a smoother transition and I could feel the extra power. This certainly beats paying $1000 like other exhaust.


          Year: 2011 Submodel: GT Alpharetta, GA, USA

          Helpful (9)

        • 4/5

          Installation Time: Shop Install

          March 24, 2012

          Mid pipe + flowmaster muffler= The perfect exhaust sound.

          It took less then 2 hours to install the mid pipe. Fits good. Sounds great. No raspiness which is a big plus. Its a great combination for your money. Intake - midpipe- axle backs and a tune from Bama Performance makes a huge difference for the 2011 Mustang GT. The car is still drivable . The exhaust is not too loud . Its just right.


          Year: 2011 Submodel: GT Venice ,Fl

          Helpful (6)

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