







Distributeur:Fabspeed Motorsport
Fabspeed Porsche 981 Cayman GT4 / Spyder Valvetronic GT3 Muffler Conversion Kit
FS.POR.981GT4.GT3CK
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.
SOUND:
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.
POWER:
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.
FEATURES:
- 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
NOTE:
- OEM GT3 center muffler is NOT included. Get the Fabspeed GT3 center muffler its bullet-proof.

Fabspeed Porsche 981 Cayman GT4 / Spyder Valvetronic GT3 Muffler Conversion Kit
If you have any questions, you are always welcome to contact us. We'll get back to you as soon as possible, within 24 hours on weekdays.
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Shipping Information
Most in-stock items ship within 2–3 business days from our U.S. warehouse or directly from the manufacturer. Custom or made-to-order parts may have extended lead times, which will be noted on the product page.
Once your order ships, you'll receive tracking details via email.
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Customer Support
Need help with fitment, product details, or installation? Our team of enthusiasts is here to help.
You can reach us anytime through our contact form or at info@houseoffuel.co — we typically respond within 24 hours on weekdays.
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FAQ's
Common questions are answered directly on our [FAQ page], including details about shipping, returns, warranty coverage, and how to verify product fitment.
If you can't find what you're looking for, just reach out — we'll make sure you get the right information before you order.
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Contact Us
Have a specific question or request? Use our contact form or email us at info@houseoffuel.co.
We're available Monday–Friday and typically respond within one business day. For partnership or dealer inquiries, please include your company information and brand interest.
FAQs
Please read our FAQs page to find out more.
How do I know if a part fits my car?
Every product page includes detailed fitment information covering model, year, and variant. If you're unsure, reach out to our team with your VIN or vehicle details — we'll confirm compatibility before you order. Our goal is to ensure every part fits the first time.
Are you an authorized dealer for the brands you carry?
Yes. House of Fuel works directly with our manufacturing partners and authorized distributors to guarantee 100% authentic products. This ensures you receive genuine parts backed by the full manufacturer warranty and support.
How long does shipping take?
In-stock items typically ship within 2–3 business days. Lead times for made-to-order or imported parts vary by brand, and estimated delivery windows are listed on each product page. You'll receive tracking as soon as your order ships!
What is your return policy?
We accept returns within 14 days of delivery on new, unused items in their original packaging. Custom, special-order, or electronic components may be non-returnable. For all return requests, contact us first — we'll help you through the process quickly.
Can I order a part that isn't listed on the site?
Yes. If you're looking for a specific brand or part not currently on the website, send us a message. Our sourcing team can often locate or special order it directly from the manufacturer or distributor network.

