My basically stock (hi-flow air filter/ RB cat back) 133k miles T2 whistles when the boost comes up. It sounds like one of those toy noise makers where you blow into a tube with a little turbine in it. I would suspect worn turbo bearings, but it sounds more like a high pressure air leak.

Any experiences with this symptom? Suggestions?

PS: so far Baby runs fine.

 

Are you sure this isn't just the normal sound of a turbocharged car? The turbo normally makes a whistling sound, probably louder now with an intake

 

are you getting the same amount of boost as you usually do?
if so,that would mean you have no leaks,and that might mean the turbo is gone.usually it will whistle if the bearings are stuffed causing also the wheel blades to touch the housings.try moving the blades and see how much freeplay you have.i would say its the turbos.

 

I bought her used (129k mi) a year ago. It had the noise then, so I don't really know if there should be more boost available.

I'll get into the turbo and try wiggling the vanes to check for play in the bearings.

What's the least costly way to refurb or up grade the turbo?