I have an 07 ss, supercharged obviously, and noticed lately, when my music isnt turned up to high, that at low speeds at around 10 hg of vac i get a slight whistling sound. It doesnt seem to be rev related, but more boost related or in this case vacuum. Im not sure to me it sounds like a wastegate closing/opening, which wouldnt make to much sense, seeing is idk how i would hear the wastegate open at 10 vac unless theres a leak somewhere. Any ideas are appreciated.

 

It's a bypass valve. No wastegate here.

 

I'm just now experiencing this same thing and occasionally under heavy load, the supercharger sounds as if it's pulsing. I'm also overboosting now... I hit 20psi last night! I normally only get to like 17-18 in the cold.

 

clogged cat. stock downpipe? if so your flexpipe has a pinhole leak in it usually only noticeable under boost.
sounds like an air leak.

 

My car has that slight whistle as well, but only after i come home from a day at the strip or a long trip where my engine was working hard. It always goes away after couple days. I figured sooner or later someone would post on here something like what i was experiencing.

 

um boost bypass mod? .

 

mine started doing it a few weeks ago, tuned out to be a vacuum leak on the brake boosted hose, had a small tear in it where it met the blower, so i trimmed it and put it back on