I've got a higher pitched sound that I can only hear when I'm in drive heading down the road. As soon as I let off the throttle the noise goes away. Definitely not loud/high pitched enough to be a squeaky belt. I don't really hear it until the engine is up to operating temp either. Automatic transmission if that helps.

I can't recall ever hearing this before in any other rig I've ever owned and a search of the forums doesn't provide any insight to this particular noise. Hoping someone can provide some assistance.

Pic for attention:

 

Things to do:

Make sure all your intake manifold bolts are snug and haven't loosened up, especially the top ones.

clean the throttle body and IAC per the following link.

http://cruiser54.com/?p=60

 

Thanks for the tip Cruiser. Will try that while I'm revamping the heater core.

 

I have a similar sound. When temps are below freezing (10 to 20F) and engine warms up I get a high pitched squeal, thought it was a vacuum line that acutated (vapor canister) but disconnecting vacuum line doesn't stop. Thinking it
might be the belt tensioner pulley but haven't tried changing that yet. Very hard to tell where it's coming from. FRUSTRATING.

 

Use a long screwdriver. One side goes against the suspected noisy spot, the other side gets jammed against your ear. It's like a cheap stethoscope. Or a long piece of rubber hose works the same way. Just prod around with it until you find the loudest spot.