Volvo Repair: S60 performance, s60 t5, service rep

Question
I have a 2006 S60 T5 and sometimes i lose power.  i will try to pass another vehicle and it feels as though the turbo stops working, but i cant be sure.  i can still accelerate, but very very slowly.  i dont hear the turbo whistle, and sometimes if i tap the accelerator i hear a metallic screaching noise for just a second, as if the turbo gets turned on suddenly.  during the screaching, power returns briefly.  it happens most often on the interstate with hard driving.  power will return after a pitstop or if i take it easy for a bit.  the dealer is stumped because they cannot reproduce the problem.

Answer
Jeremy, thats an interesting one. Car is under warranty so I think the dealer needs to call the service rep to help on this one.  I cant say that I have seen this one yet but just to be sure, I would check all the turbo hoses to see if there arent any holes in it.  May also be a ECU problem that is intermittent.  Keep going to the dealer.  There is a problem somewhere.  Roger