Milltek Sport Volkswagen Golf R Large Bore Decat Downpipe & GPF Bypass (Mk8)Milltek Decat Downpipe With OPF Bypass works great as a stand alone exhaust modification and when paired with the Milltek Mk8 Golf R OPF Back System. Removing the factory OPF and catalytic converter has huge benefits in terms of airflow and exhaust sound. By bypassing these restrictive components, back pressure is dramatically reduced. Not only does this make your system sound amazing for an affordable price, it also unlocks far higher potential for