The 140 kPa in your document makes more sense since it is about 20 psi which is what we all think is the max at high altitude (and we have all seen 15 to 16 psi). Don't know why the troubleshooting document I have refers to 12 psi max, which is why I added the (???). Still doesn't change the solution to the problem of course.

 

I now basically how a turbo works, but am not familiar with the deep science of it all. That is a G.M. document, I can not prove it or dicredit it with my own knowladge, but it IS from G.M

 

so what's up, what did you wind up doing about it Tony?

 

I'm going to take it to the dealer Monday. I watched it again tonight and I get no more the 5 psi in any gear running all the way up to 5500 rpm. It goes to 5 psi and stops it also feels like the power stops coming on also. I noticed a whisteling noise tonight while cruising at about 70 mph.
So I'm gonna take it in and take the service advisor for a ride to show them what it's doing.

 

maybe the waste gate is opening too soon.
which could mean the computer is having the problem not the turbo, just a guess.