I hear a distinct high pitch whistle while accelerating and decelerating. Yet it goes away when the clutch pedal is fully depressed. Any idea what is causing this, and how to correct it?

 

CAI by chance?

 

No CAI; stock air intake. Only change was to swap out the TCT to a Billman250 Gen X TCT last year.

 

Is it possible its more of a whine than a whistle, as in diff or trans whine?

 

Must be your blow-off valve.

 

I don't mind turning a wrench, yet I'm not familiar with a blow-off valve. Is that the official name in the Service Manual? Where do I find this shrill whistler? It's not a whine, it's a whistle that rises with RPM and lowers as RPM falls. High pitch and shrill.

 

HaHa! A blow off valve is a mod used with some turbos. We obviously don't have one (unless your S is heavily modded). It allows excess boost to blow off, and makes a sort of whoosh sound when it does.

If its truely a whistle, and it goes with rpm, its some sort of air leak. Probably on the intake side (exhaust side would be a different sound).

Suspects would include anything rubber, intake hose, vacuum hoses, etc. Also anyplace in intake there is a gasket. TB, IM, etc. Also the pcv valve. You get the idea...