Genuine BMW G87 M2 M Performance Titanium Exhaust System & Diffuser. 1x 18.30.5. 1x 51.12.5. B54 REAR DIFFUSER M EXHAUST. 4x 18.30.5. A86.350 EXHAUST TIP BRONZE. From the racetrack straight to the road: the lightweight valve exhaust system with a titanium rear silencer generates a highly emotive sound redolent of racing sports. It has