Turbo whistling? bad?

[DrBob]

Hi guys, my first post.... this site is great - lots of good information. Gotta question(s) for you... 1999 2500 auto, a/c, 4.10 rearend, 5.9 24V, about 130k, Holset HX35W turbo, ISB 215 model engine, stock tires, stock everything! I just started getting a bad whistling noise. it comes on strongest under acceleration and minimizes while at a constant load. starts around 1400 rpms. gets worse when the engine warms up. seems to minimize after about 2100 rpms. doesn't seem to be grear specific or rpm specific but more prevalent when a demand on the engine occurs. difficulty trying to elicit it in park with no load but can hear it slightly. Checked exhaust manifold bolts and they appear tight. checked all the clamps arounf the turbo and they were tight. even sprayed soapy water on them to look for bubbles. took the intake boot off the turbo - some black soot but not real bad. no evidence of oil. blade had described play but it didn't rub against the housing. no abnormal exhaust smoke. it really sounds turbo related because when accelerating and letting off the throttle i can hear what i think is the whistle from the trubo spooling down. this is a new noise? any ideas? thinks its my turbo unit? thanks for your input.....