I think I am having an air leak somewhere between the turbo and the air intake on the engine. Symptoms:
When the air temp is under ~60 deg. I get another whistling sound that is somewhat in tune with the turbo. As I accelerate and the boost builds, it gets louder. When I let off the pedal, it goes away. It seems to only happen when the engine is demanding air. When I really press it, it seems to lose power.

I do not notice these symptoms above ~60 deg.

I have checked the connections that I can see around the intercooler and air intake system, etc. and everything is tight as far as I can tell.

Any help is appreciated!

 

Have you checked your manifold and turbo gaskets?? I have see what you are describing happen in those areas.

 

I have not checked that far into it. Where are the gasket(s) on the turbo? under the clamp on the pipes? I had it into the dealer for this issue and they said they tightened everything up and I thought it was gone but when it turned cold again it came back just as bad as ever.

 

Manifold gasket is between manifold and head. Turbo flange gasket is between turbo and mounting flange. Its possible your intercooler boots are leaking under higher boost numbers. They will look fine and clamps will seem tight upon inspection. Do a search, for boost leaks. There are a few threads explaining how to check for leaks under pressure using shop air.

 

Perform a boost leak check. Its pretty simple to do. If you have never done one before, a quick google search will get you pointed in the right direction.