Never been opened as far as I know. Going strong and I'm estimating at around 95%+ of its original power. Bought it at 297k, now at 357k, aiming at 400k for 2018.
It's the M52B20TU so the smallest displacement with the lowest torque so the main and connecting rod bearings last a looong time as long as it's always warmed up.
Only things I replaced is the ignition coils/spark plugs and oil changes. I will have to take care of the crankcase ventilation some time soon. It's regularly moved above 4000rpm over long distances so I don't have any slush in the engine and the CCV valve is working but there are some cracks in some of the rubber hoses.
That's really impressive, you also know a thing or five about motor mechanics :) Let's hope it lasts 500k+ Thanks for posting! I've followed for future car related posts hehe... Keep well!