Having done a lot of porting, testing on a flow bench, and real life 1/4 mile testing I can tell you that a lot of people over do it and that flow bench results don't necessarily relate to real life. Loss of air velocity and fuel puddling can occur when hogged out beyond a point, fuel / air separation with a little change in shape the wrong direction, and polishing can exacerbate the fuel / air problems and puddling in areas that change cross section. Just look at how the small port / valve Cleveland heads when put on a 302 Boss incarnation will run circles around the big port / valve Cleveland heads in real life with much smoother idle, low, and mid range power due to less fuel puddling and higher port velocity. Unless of course you are running a 7K to 9K power band then the large port heads shine. Same with the Ford FE high riser heads vs the medium riser heads. Just sayin'