I got an oil change at a certified GM dealer, knowing they would look over it trying to sell services to me, and he said my valve cover gaskets, sc gasket, LIM gaskets, and possibly my head gaskets were bad. The car makes full boost and doesn't ever feel like a dog, do you think my head gaskets are still good? I'm not afraid to pull the heads off while I am doing all of this other stuff just to be safer than sorry.