Is your hole nice and round or kinda oblong or egg shaped.As the drum is spinning around if you dont hold pressure against the torque of the motor your hole will be off center a little.Not sure if this is what you mean or if ya mean the edge of the pulse hole is so sharp it cut the gasket.If this is the case sand the sharp egde flat.Take the intake manifold and sand the whole thing flat on a piece of sandpaper on a board.