Dinan Free Flow Axle-Back Exhaust - 2016-2020 BMW 340i/440iDinan engineers designed the F30 340i and F32 440i 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. Not only is the tone improved but the additional burbles and pops that come with it are simply intoxicating. Dinan also incorporates a Helmholtz chamber design that reduces resonance