GM-GMC: Engine Noise At 1500 RPM, power steering pump, field rep

Question
I have an 2006 take with a 305 V8. The egine produces a whine noise at 1500 RPM and higher.  It does not matter if the truck is moving or not.  It is under warranty still, so I have taken it to the dealer for service twice already.  They have replace the power steering pump, the alternator and the idler pulleys.  Still, the noise persists.  Does anyone have any ideas what is making this noise?  The water pump, the fuel pump, and the AC are the only components left that have not been replaced. I am not sure how many parts the dealer is going to be willng to replace.

Answer
if the dealer gives you crap call gm set up a case and believe that the dealer will get it fixed ... this is only if they give you trouble start asking to talk to their field rep they hate those guys to interfere

as far as the noise they are on the right track i guess all of those things can cause that noise but maybe its like the throttle body or the thermostat housing tell them to think outside the box