Lately I've been experiencing a high rpm power loss on my wagon, like it will go pretty good until I try to use boost to pass on the highway, then it kind of refuses to accelerate past 3000 or so rpm. This car used to go pretty good all the way up to 4500. The engine still revs, but the power just isn't there, and it sounds like it's running lean once it gets above 3000. I've spent countless hours checking everything I can think of, with no luck, but today while idling the car down after a long drive I noticed a horrible noise coming from under the car, kind of an amplified fingernails on a blackboard kind of sound. I've heard lots of groaning volvo pumps before, but never a racket like this. It seems to me that my high rpm power loss is a pretty likely symptom of weak fuel delivery, and I've read on the board that the in-tank pump can fail causing the main pump to groan, but I haven't seen mention of a noise like this. Is this more likely to be a failure of the main pump? It really sounds like it's dying a horrible painful death, not like it's simply being overworked.

Some details:
-fuel pressure ok at idle
-lambda ecu, freq. valve, o2 sensor, fpr all good
-boost enrichment switch works, and gets it's signal to the freq. valve.
-no major air leaks
-turbo quiet and all nuts/bolts are tight
-boost gauge showing ten psi, car not accelerating past about 5psi
-no exhaust restrictions