At partial throttle my car is making this extremely high pitched noise that sounds similar to a turbocharger. Goes away when I give it more throttle and start to hear the S/C whine. Took off my NW intake thinking it was leaking somewhere, tested it with open throttle body and the sound was twice as loud. When my car was at a mercedes specialist (accidentally yanked the S/C signal wires when changing alarm siren) he said it was normal and he didn't notice anything wrong. I checked the Y pipes myself they seem fine. Also my car runs fine at idle. Any ideas??