You guys are crazy... I went through 3 sets of headgaskets before i finally o-ringed them and haven't had a problem sence. I still think if Jesse would have o-ringed his heads his car would still be turbocharged. Yes im on a stock block and yes the car was tuned.. I can post dyno graphs to show you.. If your going to be putting boost to the heads i recommend o-ringing them. If your going to pushing a ton of boost i suggest getting the block o-ringed too.
There are so many guys right now getting away from forced induction because they are blowing headgaskets. I would be willing to put money down that if they would have o-ringed there heads they wouldn't stray. (talking about the guys that haven't had there heads o-ringed)