grinding on the cast iron cylinder takes forever, so get a dremel and dont expect it not to break. the most effective bits i found were the thin grinding disks and small metal high speed bits.
i think raising the base gasket gives high end and lowering it gives low end.
dont mess with the exhaust near/ after the stud, just the port.
dont worry too much about smoothing the exhaust either, it will just get carbon build up.