I've noticed a slight whine/whistle coming from the engine compartment of my 2002 Disco II at low RPM's that sounds similar to a turbo and changes tone along with throttle up to around 2500 RPM's or so. Any ideas? I saw a similar post mentioning alternator bearings, but this sounds almost like a whistle.

 

Alternator bearings is what first came to mind when I read the subject title. Frequency changes with RPM swings. I wouldn't throw an alternator on there with out first determining for sure that is the culprit. Those things aren't cheap.

Stick a long screwdriver on there and around that area listen through it like a stethoscope to try and isolate the nuisance.

 

Just hit VTEC yo!

 

since new (2000) my DIsco had a whine... it sounded like the ambient sound on STAR TREK (the original--I am old). I loved it. And then I replaced my idler pulley... It went away and sounded like a POS DIsco II.

Could be bearings in a pulley.

Could be a hole in the intake or a vac line.

 

Mine was loud, and was an idler pully.