While I don't have blow off valves, I do have the k&n intake and it's very loud under a heavy boost dump. I'm sure actual bovs are louder, but seriously mine is so loud without them I don't think I'd want it to be louder. Certainly not for an additional $500. If you have them and you love them I am not gonna argue with you, I'm sure they are great. For others though, get the intake first and see if you really need the bovs. My car buddies cannot believe mine are the factory diverter valves, its that loud.