bad sqealing sound from motor..

I took my gt40 upper intake off last week to re seal the valve covers. Ever since I put it all back together im getting a loud squealing sound mostly at idle after it warms up. It will go away when you rev it and come back when the RPM's fall back down. Is this a vacuum leak? Could i have put the upper back on wrong? it almost sounds like a blower wine and im sick of people asking1

any help is appreciated, thanks