Well! I don't do it now but years ago to get about 2-500K more from an engine I use to polish the complete fuel Tranfer ports.
IE. Using a pencil eraser on a dremel extention polish the Carb of any flashings all the way through to the crankshaft. Crankshaft same thing all the way through to a High sheen. Engine transfer ports/side of case High sheen again.
Rossi's I use to match the exhaust port of the exhaust to match the exhaust port of the engine. But this required cutting and I soon quit as this was a modification not polishing!