| I tend to think fuel is your culprit. The blockage in the oil feed line may have starved the turbo of oil slightly (although it sure doesn't look like it), but I have a hard time visualizing oil starvation leading to this type of catastrophic failure on the turbine shaft, especially if you take a look at the tiny 0.035" hole that the restrictor uses to regulate the oil pressure to the turbo. What I can imagine, is the force generated by a multitude of explosions (backfires) creating enough force inside, or upstream from the turbine housing to sever the turbine wheel. Coincidentally, the oil seals in that turbo would have likely been early casualties of those pressure spikes. It may be related and it may not, but if both banks of cylinders are/were backfiring in that manner, those pressure waves could also be the cause of the failure in the seals on your other turbo as well. On my Silvia I had a boost controller mishap and for only an instant I hit 36psi on the GT2871 turbo (brand new), and that was enough pressure to pop the oil seals on it (I did NOT have the prescribed 0.035" restrictors in place, I do now). I think with all the backfiring you've described, I'd also check the compression and do a leakdown to find out if your engine suffered any other ill-effects of the mis-fires/backfires. I look forward to seeing what else you discover as you guys continue your search for clues. I know you, Bernie and those of the NoVA crew helping out will get to the bottom of this, and I'm glad to know you've got some good folks in your corner!
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