dont make it to big!!!! and dont polish it, it needs to be a rough. wut big bore and wut carb u runnin? if a 88 s stage or sumthing like it then make the intake about 19-20mm and same for exhast, and match the intake to that. also, when u do it, make the port as strait of a shot as possible, so shave the one side of it but not the outside its like a turn on the track, if u could cut the track ona 90 degree turn where would u go? inside of the tire, banner, etc. to make it striat, same with ur ports. make it strait, make it big but not to big, and dont poilish it.