Well i'd say that it's not the head gasket then, if compressions fine as where water would come in to the cylinder through head gasket, the pressure would certainly go out... only other thing could be cracked head allowing water into cylinder on downstroke, does it do it when cold/hot?
If it's white smoke, i'm sure it's water, though if it's blueywhite smoke then it's oil, which if the compression is ok, must be the turbo... whats the history?