I have a 2001 A6 2.7T, 6 Sp Manual, APR Chip, APR R1 diverter valves, ABD big bore intake, 85K miles
The problem I am having isa whistle noise when it starts to build boost only does it at 1-3 psi and then stops still builds boost to 16-17 psi no problem or lose of power. Hard to tell were the noise is coming from.
Any ideas what this could be? Turbo going bad?

Thanks Aaron

 

Bearing maybe?
Anyone?

 

If by whistle you mean an air noise (versus a metallic noise), I would suspect some sort of air leak. That's just a guess from a semi-technical guy. You do have heavy duty diverter valves, so they can probably be ruled out. The only other thing I was warned about when I chipped mine was the throttle body boot.

Good luck. Let us know what you find.

 

It sounds like a vacum leak to me,I need to go through and check all of them.I thought it was possibly the diverter valves at first so that was a good excuse to go ahead and upgrade. But that didn't change anything as far as the noise was a noticable difference otherwise.I have a Samco throttle body boot that I haven't installed yet.
Guess I will try that next if that does nothing, off to the shop it goes.