Remus BMW M3/M4 Racing GPF Back Exhaust System (G80/G81/G82/G83)Remus BMW M3 M4 GPF Back Exhaust System is a state of the art exhaust system for the G8X platform. This is the same system as the racing rear silencer axle back system with the addition of a front silencer replacement tube between the axle back and the vehicle's GPF. The addition of this mid pipe offers a further reduction in back pressure, slightly higher tuning potential and a greater enhanced exhaust note. The Racing Rear Silencer offers: 6mm