Milltek Large Bore Downpipe and Hi-Flow Sports Cat - BMW 2 Series M240i Coupé (G42 XDrive OPF/GPF Models Only)4. 5inch Downpipe with 90mm Flex & 200CSPI Euro 6 Cat Fits to Milltek Sport and OE Cat Back Systems Requires Stage 2 ECU Remap Our range of Cat Back systems are perfectly suited to cater for anyone looking to improve their sound and aesthetics, designed as a direct replacement for the original system, available in multiple configurations enabling the owner to choose the increase in volume of their exhaust and or add a more suitably aggressive tone.