Well I’m no expert porter but I’ve done it enough I think I do alright. I think changing the timing and adding compression is where most the gains come from. But after that it would be port shape and polishing. I shape ports for more flow, transfers I like to have them open on the intake side first and point them that way. The lowers usually get opened up some to flow more. Every saw is different. Not really one answer to this question. Some require very little grinding and others a lot.