Active Autowerke BMW M3/M4 Equal Length Midpipe (F80/F82/F83)Active Autowerke equal length exhaust mid pipe for the BMW F80 M3 and F82 M4. The Active Autowerke equal length Mid Pipe was specifically designed to eliminate the highly restrictive nature of the S55's factory exhaust system thus creating optimal exhaust flow and drastically improving performance. Engineered for an exact fit on the BMW F80 M3 and F82 M4, the difference in power and throttle response with this mid pipe will be noticeable the moment it