Active Autowerke G80 M3 and G82 M4 Valved Rear Axle-back ExhaustG80 G82 BMW M3 M4 Rear Exhaust Active Autowerke is proud to release the Active Autowerke Valved Rear Exhaust for the BMW G80 M3 and G82 M4. While these cars have received rave reviews for their performance, the sound is a muffled one leaving the driver to wonder if they are really driving a BMW M car. In order to solve this, Active Autowerke has created a full exhaust system for the G80 G82 which comprises this rear axle back valved exhaust, a mid