Remus BMW M3/M4 Racing Secondary Cat Back Exhaust System (G80/G81/G82/G83)Remus BMW M3 M4 Racing Secondary Cat Back Exhaust System is a high quality, hand crafted racing system that runs from the secondary catalytic converter all the way to the tips. This system bypasses the factory OPFs, but leaves both cats in place. The secondary cat back exhaust removes the resonated mid pipe and features a much more efficient design for better airflow. The backbox has been completely redesigned into a twin silencer setup and when the