as for the headgasket, the factory mls gasket is fine, i have boosted 28psi on many of occation without any problems. Also remember to use ARP head studs n/ shit, cause under extreme boost conditions, the head and block can actually pull apart with shitty studs, or so i hear. as for the piston rings, i cant help you out there, anyone else? I know the rings arent usually the problem though, its mostly a cracked piston or throwing a rod, but thats not to say ring failure is non-existent.