Every psi of boost = 11 degree's. 20 PSI is 220 degree's above ambient. If its 30 degree's outside that 250 coming out of the turbo. Then you have the coolant temp is lets say 165 degree's. The intake manifold is at 165 degree's. Anyone who has put an IAT sensor inside the intake and let the motor get nice and hot will see this effect.
Yes that 250 temp will get cooled down quite a bit by the intercooler.. But your reaching for straws. I'd bet there is something else at play. Improper tuning is my bet(tuned way lean). But with no datalog.. I cannot prove/disprove the theory, neither can you. Now your going through the carnage looking for a smoking gun to point the "Ahh HA... " finger. Simple Buick 101 tuning.. it gets cold outside.. crank the fuel pressure up. This has been done since the 80's.
Plugs being destroyed means the motor detonated.. plain and simple. Why did it detonate?? No datalog= your guessing. There are 4000+ alcohol kits(mine, SMC's, Devils Own, Snow, etc) running around on these cars. Everytime something goes wrong its the alcohol kit. (I wont get into running a motor hard with a really old kit)..You beat on a motor enough times it will poop the bed sooner or latter. Thats "racing". This is why there is no warranty on racing engines. Too much is at play. And like will all games... you run really high boost on a V6.. hedge your bets. But this strategy costs money buying extra stuff and using it. At this point I feel bad for the guy that lost his motor, and the truth is the best thing that can happen is to make the proper decision as to what happened so he can have closure and move from there. But before the finger wagging starts.. better be sure on your predictions and not "assume" the problem. That doesnt fix anything. Worse is an improper diagnosis.. put an engine together.. and kabooom... the culprit showed its head again. Its always the little things that do you in.