Most gaskets have openings larger than the ports they are meant to cover. If the port has enough metal, you can get increased flow by enlarging the port to the same size as the gasket opening. You will want to do the port on each side of the gasket to get the full effect.
Areas that this is usually done involve air/fuel flow. Intake ports between the upper and lower intakes. Intake-to-heads is another area. Exhaust ports usually need little if any matching.
I would suggest having this done by a professional.