Put a new air horn on my 07 M8 last year. Lets alot more air in ! To say that i notice a big diff. No,but I think there is proablly some tool out there that could measure the diff. I allso put on a new Y-Pipe this year .The M8 is alot crisper .I will have to put back the old air horn and see if i notice a diff. and let you know in the future.