i did the head port polish , 10 3/4 piston bigger valves and stud kit and mudbuster cam stage II (( still 660 bore)). It made a little difference but not as much as i hopped the power is now good from bottom end to top and on the dyno the power curve is almost flat. Before the mods it would peak then fall off. I still have a stock carb , single FMF muffler on a stock pipe with a intake that is outside yhe engine compartment with a uni and a 205 main jet, and it run 13 to 13.5 with the mass air sensor
thats my two cents
This combination's potential is not being seen, IMO. The exhaust is restricting it like crazy. Exhaust on a stock engine doesn't do much, but on a motor with those mods, it does.