Milltek Sport BMW M3/M4 Resonated OPF/GPF Bypass Mid Section (G80/G81/G82/G83)Milltek Sport BMW M3 M4 Resonated OPF GPF Bypass Mid Section replaces the factory OPF filters to reduce back pressure and increase flow. In doing so, your G80 or G82 will see quicker throttle response and faster turbo spool. This results in improved low and mid range torque without sacrificing top end power. The OPF Bypass will also unlock greater tuning potential. As this is a resonated Mid Section, the pipework features a single resonator that helps