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Fabspeed Porsche 991 GT3 / GT3 RS Rennsport Muffler (2014-2016)

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Calculated at Checkout
HP (whp) / (crank):
+16 / +18
TQ (ft/lbs):
WT (lbs):

The ULTIMATE OEM style high performance replacement muffler for your GT3!                                                                                           

As many GT3 owners know, the OEM mufflers are prone to cracking, breaking and blowing out, particularly the titanium mufflers on GT3RS cars. We wanted to design a muffler replacement that not only fixed that issue but also improved on the OEM design. Using our 25+ years of air and water-cooled experience, we took the valve open tubing to 2.75in / 70mm which is the optimal diameter for GT3 engines to have low restriction but maintain high velocity and high GT3 pitch for the signature GT3 CUP car sound. Then, we implemented our signature investment cast X-Pipe for optimal exhaust scavenging. The X merges the two cylinder banks without creating any restriction in exhaust flow. To maintain the factory muffler’s exhaust note and lack of drone, we mimicked Porsche’s 7 chamber design. This makes for a completely drone free muffler, even when running catless race headers! Pair this with our Side Muffler Muffler Bypass Pipes for the ultimate emissions compliant GT3 exhaust. This muffler is guaranteed to NEVER BREAK or fail.


This muffler will have a very similar tone to the OEM muffler, however, it will be a bit louder with PSE turned on. It will also sound a bit smoother and higher pitched thanks to our signature X-pipe.


On our 991.1 GT3RS test car, paired with our Side Muffler Muffler Bypass Pipes, the Rennsport Muffler picked up an impressive 27 ft/lbs of TQ down low at 3,200 RPM. From 2,900 RPM all the way to 5,700 RPM it picks up 10 WHP or more, and peak WHP is up from 446 to 454! That’s a gain of 8 WHP or 9 HP at the crank.


  • Fits all Porsche 991 GT3 / GT3 RS vehicles 2014-2016 worldwide
  • Constructed from CNC cut T304L stainless steel
  • Designed from 3D scans of the OEM muffler so we can achieve perfect bolt-on fitment
  • Will not break or crack like OEM GT3 mufflers do
  • Incorporates our signature cast X-pipe for superior flow and exhaust scavenging
  • Paired with our Side Muffler Bypass Pipes this muffler adds +27 ft/lbs of TQ and +16 WHP or +18 HP at the crank!
  • 3 different tip options available
  • Completely retains PSE valved exhaust functionality
  • No Check Engine Light guaranteed
  • This cat-back system is emissions legal in all 50 states and the rest of the world
  • Built in house at Fabspeed Motorsport USA in Fort Washington, PA
  • Simple bolt-on installation, no cutting or welding required
  • All Fabspeed performance products are backed by the Fabspeed Lifetime Warranty


  • Requires OEM gaskets and hardware to be reused
  • If they are not available here are the necessary part numbers. 
  • 2x Muffler band straps (99711111970)
  • 2x Bolt for muffler band strap (90006736201)
  • 2x Each Side Muffler to Center Muffler Gaskets (99711156390, 99711156190)

Returns Policy

To RETURN any system, product or merchandise you must contact us first for a Return Authorization (RA) Number. Special order and custom made systems, apparel, Carbon Fiber Wall Art, and other certain merchandise are NOT returnable. ALL SALES ARE FINAL. To return a Fabspeed Motorsport product an RA number must be requested and if granted the item(S) must be in original Fabspeed Motorsport sealed packaging. A copy of the original invoice and a brief explanation must accompany all returned items. You must follow our instructions for returning items carefully, or Fabspeed Motorsport reserves the right to charge a 25% restocking fee on any OPENED box or repackaged products. Customers are responsible for return shipping charges. If an order was shipped with a promotional “Free Shipping”, and the order is returned, we exclusively reserve the right to charge the customer or distributor for the cost of that original shipping and handling. If a Fabspeed Motorsport Performance package is ordered, and an individual component of that package is returned, Fabspeed Motorsport reserves the right to charge back the performance package discount along with any additionally offered discounts. Return shipped items DAMAGED in transit will RESULT in additional charges up to and including rejection of the competent. It is the customer’s responsibility to ship safely and properly. No returns accepted after 30 days from the invoice date. No credits will be given after 30 days from the invoice date.

To qualify for return, the product must be unused and remain in the original packaging, as well as match the current design and packaging for the product at the time of return. Sounds is subjective and therefore does not qualify for a return of a used product. See Sound Solution Guarantee to see if your product is covered.

Periodically mistakes are made when ordering, or a wrong part is shipped, and you may wish to return an item. We will do everything reasonable to satisfy you. Please contact Fabspeed Motorsport immediately via email at to discuss the circumstances before returning any products. Anything returned without prior authorization from Fabspeed Motorsport will be refused. All returns must be sent back fully prepaid. Our customer service department ( will issue a Return Authorization Number, which must accompany any return. A copy of the original invoice and a brief explanation must accompany all returned items. No returns accepted after 30 days from the invoice date. No credits given after 30 days.


Fabspeed Motorsport cannot be held liable for refusal of, delay of, loss of, theft or damage to a shipment of any item. The customer agrees to indemnify Fabspeed Motorsport for all costs, fees and expenses Fabspeed Motorsport incurs as a result of any violation of any local, state, federal, national or international laws or regulations. Customer agrees to take responsibility for lost packages that were not independently insured or sent without requiring signature. The customer understands they will be liable in the event of additional fees, tariffs, or legal issues such as border seizure. Customer accepts these risks and agrees to release Fabspeed Motorsport of all liability.

Fabspeed Motorsport reserves the right to charge a shipping and handling fee on every order being shipped from our facility. This fee is universal and applies to all retail and wholesale purchases and cannot be waived or credited.

A 6% sales tax will be implemented for every purchase made by a Pennsylvania resident. This fee will be charged for in-house installations and products purchased online, over the phone, and/or via email, this fee is required by law, is non-negotiable and non-refundable.

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