soft high pitch noise

[ApacheX]

Hey guys, just wondering if anyone can help us out here

at about 1500 - 2000rpm, i get this annoying high pitch sound. Usually only happens at slow speeds, but when im at around 50ish and im sitting between this rev range, there is the really high pitch noise. not running any boost at that point either, so i doubt its any form of spooling. any suggestions?

[dangerous_daveo]

I occasionally get this too. At first we thought it to be a vacume leak, but we never found one (doesnt mean it isnt a vacume leak tho)