Since 2020, Porsche’s 718 Boxster GTS 4.0 and Cayman GT4 models have carried the burden of gasoline particulate filters. While essential for emissions compliance, these filters rob the 4.0-liter flat-six of its voice, dulling both volume and tone. The Porsche 718 Cayman GT4 exhaust systems from Milltek Sport are designed to address this issue. Available for both manual and PDK applications, the lineup ranges from refined valved systems to aggressive GPF/OPF bypass configurations, giving owners complete control over how far they want to push performance and sound.
For those who want a balanced Porsche 718 Cayman GT4 exhaust upgrade, Milltek offers valved filter-back systems tailored to transmission type. The Milltek Valved Particulate-Filter Back Exhaust for PDK models includes dual valve assemblies, a rear silencer, and mounting hardware designed for automatic cars produced after February 2020. Manual drivers can turn to the Milltek Valved & Resonated Particulate-Filter Back Exhaust, which offers a smoother resonated tone and dedicated brackets for stick-shift applications. Both deliver a noticeable improvement in volume, tone, and throttle response while maintaining everyday usability.
These systems retain factory emissions hardware, meaning they don’t require ECU remapping and can be installed without additional tuning. Owners can choose from a wide range of tip finishes, including polished, Cerakote black, brushed or burnt titanium, and carbon fiber, ensuring the rear of the Porsche 718 Cayman GT4 exhaust looks as sharp as it sounds.
For drivers who want more character but without excessive harshness, the resonated option in Milltek’s lineup delivers. The Valved & Resonated Filter-Back Exhaust for manual applications adds depth to the Porsche 718 Cayman GT4 exhaust note, smoothing out the frequencies that can become tiring on long drives. It’s a strong choice for enthusiasts who value refinement but still want the excitement of a louder, more defined flat-six soundtrack.
Moving up the scale of aggressiveness, Milltek’s bypass-equipped Porsche 718 Cayman GT4 exhaust systems provide the most dramatic transformation. The Valved Filter-Back Exhaust With GPF/OPF Bypass for PDK cars and the Valved & Resonated Filter-Back Exhaust With GPF/OPF Bypass for manuals replace restrictive particulate filters with dedicated bypass pipes while maintaining a valved design. Both unlock a raw, motorsport-inspired tone and restore lost horsepower, though they do require a stage 2 ECU calibration to match. Marked for motorsport use only, these systems are designed for enthusiasts who prioritize sound and performance over compliance.
The result is sharper throttle response, more power through reduced backpressure, and an exhaust note that finally matches the potential of the GT4 and GTS 4.0.
For those who already own an aftermarket or factory filter-back system but want to take it further, Milltek offers GPF/OPF Bypass Pipes. These 70mm pipes fit both manual and PDK cars, pairing with OE or Milltek exhausts. Like the full bypass kits, they require a stage 2 ECU map and are designed for track use, delivering the most unfiltered sound possible.
The Milltek lineup for the Porsche 718 Cayman GT4 exhaust covers every stage of intensity. At the more reserved end sit the valved resonated systems, tuned for manual cars and offering a refined note that works well for everyday driving. Stepping up brings the non-resonated versions, designed for PDK models, which add volume and sharper character while still maintaining balance. The bypass-equipped setups move things into much wilder territory, combining resonators with free-flowing design for a deep, track-focused tone in manual form or an even more raw motorsport sound with the non-resonated PDK application. At the far end of the scale, the standalone bypass pipes strip everything back to its most aggressive, delivering an unfiltered exhaust note that transforms the flat-six into something truly ferocious. This progression makes it easy for owners to decide how much intensity they want in their Porsche 718 Cayman GT4 exhaust build, from subtle refinement to uncompromised aggression.
Every Porsche 718 Cayman GT4 exhaust option from Milltek Sport, along with the Boxster GTS 4.0 applications, is available through Bulletproof Automotive. Whether you want subtle refinement or uncompromised volume, these systems restore the emotion and personality of Porsche’s flat-six, turning each drive into a far more rewarding experience.
