High Pitch Whistling!
 

So I have a 95 Z28 and there is a high pitch whistling coming from under the hood... It doesnt happen all the time but often and when it occurs it screws up my idle making the car drop under 500 in most cases. I was reving it the other day while looking under the hood and u can hear it a lot after you do that. It seems to be coming from the right side of the engine towards the bottom. Anyone know what this can possibly be its pissing me off haha

Probably a Vacuum leak someplace , check your pcv valve too if thats clogged or whatever it'll hiss too.
But yeah certain vacuum leakes could cause your car to idle erratically. But you should get under the hood with the car running and try tracking it down.
Or spray soap and water on the vacumm hose's to see if there is a leak.

yeah, check vaccuum, also try taking off the belt and spinning each of the pulleys by hand, could be a bad bearing in one of them.

it's a vacuum leak.

Yea man..check the vacume lines.. I told u that already but u don't pay attention to me

I'm gonna say check the vacuum lines....