Whistle sound from engine compartment ?

My 1999 Exped has been whistling. You depress the accelerator and get RPM over 2500RPM and cruise a bit. Then as you let off the gas at around 2000RPM or less is whistles like a steam engine. Not REAL loud but definately noticable in the passenger compartment. I imagine this is a vacuum leak and maybe related to the automatic transmission ??? Anyone else ever have this problem ? Could it be the passing gear hose or somethinge else ? :confused:

Use a can of carb. cleaner and spray along the intake and rubber hoses. the engine should smooth out when you hit a leak. Use channel locks and pinch off the hose to the vacuum booster. When you locate it replace the defective part.

Try disconnecting the IAC and drive it...you'll have to hold the throttle cracked slightly at idle to keep it running...the Ford IAC is cool in it's construction matches EXACTLY that of a whistle, sometimes they get a little dirty and start to act EXACTLY like a whistle...for some reason I never can get them clean enough to stop being a whistle. Also, put a stethescope to the alternator, they are bad about singing. Good luck with it.

Gee thanks for the tips fellas. I think the leak I might be hearing is a compression leak. I had the vehicle in for diagnosis and one of the clyinder pressure is out of spec. prolly a head gasket :-(