$595.00 USD
$595.00 USD


















Unlock the True Potential of Your GT4 RS
While the factory rear muffler on the standard 718 GT4 wasn’t a major restriction, reusing it on the high-performance GT4 RS has created a bottleneck for the GT3-derived engine. The original tubing diameter—less than 2¼ inches—remains unchanged, restricting the increased power output. Although this design helps meet sound regulations and simplifies manufacturing, it doesn’t maximize the performance capabilities of the GT4 RS.
Our Valved Exhaust system changes the game by utilizing full 3-inch oval tubing, perfectly engineered to fit within the tight confines of the rear chassis. With a focus on performance and sound quality, we’ve designed the secondary flowpath as a Helmholtz chamber to effectively reduce drone, ensuring a smooth and enjoyable driving experience. Coupled with our Valve Controller Kit, you can maintain optimal sound and performance throughout the rev range, unleashing the raw, unmistakable tone of the flat-six engine as you push it to its limits.
Fitment Note: Due to the system’s advanced anti-drone design, it is not compatible with factory Over Axle Pipes. It must be installed alongside any of our Over Axle Pipes or other compatible aftermarket alternatives to ensure proper fitment and optimal performance.
Exhaust Tip Selection: For those looking to maintain the factory appearance, this system can be used with OEM exhaust tips. However, please note that the OEM tips feature a much smaller diameter inlet, requiring the system to be necked down, which introduces a restriction and reduces overall performance. To extract the most from your GT4 RS, we strongly recommend selecting our high-performance exhaust tips, designed to complement the full 3-inch system without any compromises.
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$595.00 USD
$595.00 USD
This product can expose you to chemicals such as lead and lead compounds, which are known to the State of California to cause cancer or birth defects or other reproductive harm. For more information, visit www.P65Warnings.ca.gov.
For a complete list of chemicals known to cause harm, visit https://www.p65warnings.ca.gov/chemicals.
Under the federal Clean Air Act (42 U.S.C. §7522(a)(3)), it is illegal to manufacture, sell, install, or use any part that defeats or alters a motor vehicle’s emission control system for use on public roads. Unless a product has received an Executive Order (EO) from the California Air Resources Board (CARB), it is not legal for use or installation on any pollution-controlled vehicle driven on public highways.
Some states have CARB-equivalent or independent emissions laws. Customers are responsible for verifying local regulations before purchasing or installing emissions-related products.
All performance, racing, or competition parts sold by this company are intended solely for off-road, closed-course, or competition use on vehicles that are never registered or used on public highways.
Kies Motorsports, LLC sells and markets these products for lawful use only. We do not condone or authorize the use of emission-control defeat devices or any modification that violates the Clean Air Act or state regulations.