I've been hearing this small whistling noise (kinda like a turbo sound)in my car and it only happens sometimes when i drive my car mostly in the morning when its cool. Its noticeable around 3500 rpm's to wot. i dont feel that it affects my car on power or acceleration. I was thinking that it might be the boost bypass valve because ive heard of people saying that they can stay open. but im not sure and was just throwing it out there to see if anyone has had the same problem.