Active Autowerke G87 M2 Valved Rear Axle-back ExhaustG87 BMW M2 Rear Exhaust Active Autowerke is proud to release the Active Autowerke Valved Rear Exhaust for the BMW G87 M2. 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 G87 which comprises this rear axle back valved exhaust, a mid pipe with equal length x