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Fabspeed Porsche 981 Cayman GT4 / Spyder Valvetronic GT3 Muffler Conversion Kit

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$2,306.95 - $2,768.95
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Porsche Boxster Cayman owners have requested a conversion kit that allows the installation of a Porsche OEM 991 GT3 style center muffler onto their cars. Fabspeed Motorsport listened and designed in CAD and built inhouse a lightweight installation kit that allows any 6 speed Porsche 981 GT4 or Spyder owner to install an OEM GT3 center muffler (A PDK version will also be available once we are able to test fitment). This kit also allows the installation of a Fabspeed 991 GT3 Center Muffler Bypass Pipe or 991 GT3 Center Mini Maxflo Performance Exhaust onto your 981 GT4/Spyder. Fabspeed ALSO has their own GT3 universal high-performance muffler that will fit as well. Its actually stronger and makes more power than a OEM Porsche GT3 center muffler. 

The system consists of 2.5" 63.5mm CNC mandrel bent one piece Left and Right side over axle pipes and clamps. Then a set of valved side muffler inlet Y-pipes that retain the factory PSE valved exhaust functionality. The valves are OEM Porsche GT3 HELICAL aerospace quality imported from Helical Great Britain. Helical limited U.K. vacuum-actuated exhaust valves are the EXACT same quality that Porsche uses on all GT3 cars as well as Ferrari, McLaren and other hyper-cars. NO CHEAL Chinese exhaust valves 100% guaranteed to fail are ever used at Fabspeed. We use our FLOW Waterjet to cut a CAD designed, lightweight, stainless steel mounting bracket to hold the muffler; hardware for installation is included. This and the Factory Porsche muffler band straps hold everything in place. For tips, you can use the factory 2007 997 to any 2019 991 GT3 tips or you can order Fabspeed GT3 exhaust tip mount with any choice of Fabspeed signature tips. Innovation and quality at Fabspeed with over 25+ years of experience. 


Enjoy the characteristic sound of a factory Porsche engineered exhaust but with a nice increase in volume! With PSE off (valves closed), the exhaust is still tame and livable in the cabin. However, with PSE on (valves open) hear that flat 6 howl up to redline! The larger over axle pipes that are included also contribute to the overall louder tone.


The 991 GT3 muffler was designed by Porsche to support 475 HP, because of this it flows a lot better than the 981 GT4 muffler that was only designed for 385 HP. We expect this increase in flow, helped by our larger over axle pipes and muffler inlets, to give a nice HP increase. 


  • Fits all 6 speed manual Porsche 981 Cayman GT4 / 981 Boxster Spyder vehicles (2015-2016). A PDK version will also be available once we are able to test fitment
  • Choose between your choice of Premium Fabspeed Exhaust Tips or use OEM 991 GT3 Tips.
  • CNC Mandrel bent 2.5" 63.5 precision over axle pipes to valvetronic inlet pipes
  • Helical Aerospace United Kingdom exhaust valves- same OEM quality valves used on Porsche GT3, GT3RS. Made with 321 stainless steel and Silica carbide.
  • Constructed from 14-16ga T304L stainless steel tubing for maximum power and durability
  • Direct bolt-on installation; no cutting or welding required
  • IF you are considering any other GT3 center muffler for your 981 Cayman / Boxster FABSPEED is your 1 and ONLY smart choice as Helical valves are included versus cheap Chinese valves from ALL other systems. 
  • All Fabspeed performance products are backed by the Fabspeed Lifetime Warranty


  • OEM GT3 center muffler is NOT included. Get the Fabspeed GT3 center muffler its bullet-proof. 

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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