Throttle noise??

I have a 98 gtp thats making a wistleing noise from somewhere in or behind the throttle body, i cleaned the throttle body today with cleaner and put a new air filter in it, but its still making the noise. It sounds like it is coming from somwhere after the plate inside the throttle. Does anyone have an idea what could be making it. Thanks

I'd check the throttle body mounting gasket. Sounds like a vacuum whistle to me.