One sure way to tell if backpressure is causing problems is to log the torque on the lower head bolts/studs. If you see the torque value on the lower nut drop(but not the top ones), then it's almost a certain bet that it's backpressure. It will most certainly drop once after it's first fired, but once you retorque them they should stay consistent.

 

Every single lower bolt was loose the last time the head gasket went. Wether or not that was due to backpressure or stretching of the TTY bolts, i don't know. I have never retorqued the head gaskets after initial install. Am i not doing this right? Should it be run and then retorqued after one heat cycle? This would be a HUGE PITA, but if its necessary....

 

Heat is being kept in the exhaust port due to backpressure and over not much time at all, through normal expansion and contraction of the head, the bolts will loosen. On most turbo cars, we do retorque the head bolts after a few hard passes.