High pitched whine from back of engine

[wreckxxx]

I've noticed a high pitched whine from the back of the engine on my B5 RS4. It's barely noticable from the cabin (spotted the noise with window open when a van was next to me bouncing the noise back at some lights). When I open the bonnet it's pretty loud. It stops briefly when I blip the throttle, but it's there when the engine is at a static rev level. It's there at idle and up through 2-3k revs (possibly beyond) in neutral and in gear with clutch dipped and part engaged. Cannot tell if it's there when clutch is fully engaged and I'm driving as the engine/road noise swamps it. No obvious pointers coming from VCDS.

Clutch and turbos are both back there - are the the turbos rotating quickly enough to generate a high pitched whine at 1k engine revs?

Any thoughts welcome. Trip the the garage likely.

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