Update. I get the truck back today. 14.5 weeks in the shop since Thanksgiving...
Turbo replaced (again). ECM replaced (again). No definitive root cause given yet, but GM's prevailing theory is a "bent rod" in the turbo...manufacturing defect. Honestly, I'm not buying it. You would think if it were a mfg defect it would show up immediately, not after 7,000 miles. I also have a hard time believing two turbos failed in the exact same way on my particular truck. Seems like the chances of that happening are almost non-existent. However, like I said before, I'm going to let them run their process and see what happens. Both the turbo and the ECM have been returned to Detroit for root cause confirmation.
Demon, thanks for the tip on the harness issue. Both the dealer tech and the GM Engineer claim they checked for that on my truck and it is NOT an issue. Demon, perhaps you can comment on what "rod" is in the turbo? Is that the rod that controls the intake opening? @DemonWorks
GM is extending my ENTIRE powertrain warranty to 150k miles, and they threw in a 36,000 mile maintenance agreement for my troubles. The truck has about 90,000 miles on it now. Since both turbo failures happened at roughly 7,000 miles, I assume if I get to 150K miles then I hopefully will be good to go long-term. We shall see. Isn't the oil pump belt needed at 120,000 miles? Looks like maybe I can skip the cost of that big service...
I know some of you will say "trade that sucker in before it breaks again!" I hear ya, but that's complicated. I'd not only be adding a truck payment, but losing the lift kit / tires / wheels (without some major hassles). Since I like the truck, and this truck is exactly what I want, I'll have to think on this hard.
My honest expectation is I will have the failure again in 5-10k miles. GM understands at that point, I'm done and they claim if it happens again, they will work out a deal with me for a new truck. No idea on details yet.
Thoughts?