first was blown head gasket a few months after purchase, probably bought it with a bad gasket. second was detonation right after rebuilding due to sticking wastegate. this time was 140 mph for about 30 minutes at 12 - 14 psi on pump gas - looking at the piston it had to be detonation but I had run it, including autocross for two seasons being very careful not to run boost too high. Whatever reason, #2 got too hot.