Can someone explain to me the difference between a stage I, stage II, and stage III port? What is the difference in hp/tq gains? what is the difference in smog? engine wear?
the hp difference depends on a number of variables. flow rate, velocity, what mods you have on your car. different companies stages flow differently. so there is no simple answer to give you.
I don't believe porting your heads will do anything to effect smog levels....cams on the other hand will put a very large knot in those tree-hugging hippy environmental nazi's panties.