Can't Find Vacuum (or some kind of) leak
 

Having some problems with what i believe is a vacuum leak somewhere. I was driving down the road, and this high pitched whistling noise started coming from my engine. It would go away when the rpm's dropped below 1500 or if i pushed on the gas pedal.

I thought it was the throttle body, so i switched with a friend of mine, still there.

Pulled the belt off and ran the car, still there.

We pulled up the intake and moved it around, made sure gasket was ok, the vacuum's lines in the back were in, and the pcv valve.

I do have a K&N oil cap breather, had for awhile, the vacuum hose is still attached to the intake elbow too.

This noise is very loud and hurts my ears listening to it. Need some suggestions on what it might be. Thanks.

Raise the idle and find it. If it's making a loud noise, how hard can it be to find? Try using 3 feet of heater hose as a one ear stethescope, if it helps.

Take care,
~Chris