Milltek Sport Volkswagen Golf R Hi Flow Sports Cat Downpipe & GPF Bypass (Mk8)Milltek Hi Flow Sports Cat 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 upgrading the factory catalytic converter has huge benefits in terms of air flow 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