Pull the inlet hose on the turbo and inspect the impeller...
Check where the down pipe connects to the turbo. Your looking for bolts that have completely fallen out or loose. If that’s the case then that’s your boost leak! The fix that GM has is new bolts, gasket and a new high temp lock tight.
Would it be possible to have a boost leak without any noticable loss of power?
Yes, it’s such a slight leak that’s why it’s whining. You won’t notice a power loss, maybe a very tiny loss. Early on this problem is always misdiagnosed by replacing the turbo. This happened 3 times with my truck until they figure out what was really causing the problem. It’s a simple fix. How many miles do you have?
Yeah it sucks…… but there’s only two bolts holding flange together. Put it on lift or grab a creeper and a flash light, look for soot. If in fact that is the problem, get new everything especially the flange gasket don’t mess around. Be aware that little bastard is razor sharp and razor thin. Mine was easy to detect the bolt closes to the exhaust manifold (heat) was always gone, see if that helps you.
This is a long shot, but do you happen to have part numbers for the downpipe to turbo bolts/studs/nuts? I've lost 3 of the 4 holding the DP to the turbo, studs and all. Looks like the studs backed out, the threads in the turbo housing look undamaged so with any luck I just need to get new studs and nuts in place but I've not having any luck finding them on the internet. I'll give my local dealer a call tomorrow and see if the parts dept can figure it out as well, I'm just in a bit of a pickle with only one stud/nut holding things together and I'm afraid if I drive it too much more I might break that stud off and really screw myself.
