Active Autowerke BMW S63 Downpipes | V8 BMW X5 M and X6 MActive Autowerke is proud to bring you our hand made Signature S63 Downpipes for the twin turbo V8 BMW X5 M and X6 M models. A turbo impeller wheel speed is mostly limited by the exhaust back pressure within the system. If one could eliminate some or most of this exhaust back pressure, the turbo will spool that much faster and effortlessly resulting in quicker engine revs and increased HP. The Active Autowerke Signature down pipesu00a0are designed