Internally, the exhaust is typical of other Dinan exhausts and is designed to improve exhaust flow by reducing back pressure, resulting in increased power output and a great sporty sound that is civilized when you want it to be, and pleasantly aggressive under hard acceleration. This is partly courtesy of the retained computer-controlled exhaust valves that limit noise during low-speed driving and open fully during high-load conditions to allow free flow. Like all Dinan exhausts, our M550i Free Flow Axle-Back Exhaust is engineered to reduce low-RPM drone so the cabin of the vehicle is still intimate and not drowned in an excessively loud tone. In fact, on the G30 M550i equipped with a Dinan exhaust, you will be astounded at how eerily quiet it is in the cabin. That is quickly changed however when exiting the vehicle and being witness to the sporty luxury sedan revving its stout V8 engine with the exhaust valves wide open. Blissfully bellowing a sweet deep tone that begs for more is the reward. When you succumb to those desires the throaty note at full load is even more rewarding letting all those around you know your M550i is seriously capable yet dignified at the same time.