Personnally i like the noise it makes, but it is very loud and does get on your nerves after driving for a while.
I've also cut a 5'' hole though the inner wing and used some ducting to feed the filter direct cold air from the fog light hole. I think that might have made it a bit louder. I can't seem to drive down the road now without frightening old ladies and small children...... but it's a grin and a half :D
I don't know if it's made much difference to the performance, but the sound it makes is awesome, and that alone makes me drive faster.
Needless to say, the wife doesn't like it..... what does she know anyway...