Dinan engineers designed the BMW 330i/430i exhaust 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. Like all Dinan exhausts our 330i/430i 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.