I did notice that the tell-tale boost gauge in the car was at 1.2bar at it's highest reading.... would this be a factor? I drove the car for a bit before we embarked on this journey, car ran great, believe it or not, and there was no smoke, noise, misfire, or anything of the negative nature.... This all began with a broken headstud

.... it's been an expensive and interesting ride from there on out. The spark plugs looked to be about 20 years old, but I cannot say with any certainty what the cause of the detonation would be. Fuel issues? Where should we start?