The polishing isn't as important as the port work itself. You aren't going to make or break a set of heads polishing alone. You are going to gain some but in a way polishing is just a cover-up for the port work that was done. If I port your heads out my secrets and years of R&D etc. are in those heads. If i port them and give them to u you know what I know and my game is up. If I port them and polish over my port work you can't see what I did and I can still eat dinner tonight. Polishing is important but not as critical as some might think. 80 grit your intakes, polish your exhaust, enjoy