How much boost do you have? Head gaskets can handle 10-12 #'s and above that one needs to "O" ring the cylinders as Jerry suggested. Before you start ripping things apart do a search for an "engine combustion gas detector". They run from $25-$50 and will show if a head gasket (or head) is leaking. Just plug into radiator cap hole and if detector fluid changes color something is leaking. You can even get fancy and test with each spark plug wire off till you find the one where the color doesn't change---that's the trouble spot.

Evan