so lets say you have a hopped up engine with a small carb, i'd imagine you can jet it to give enough fuel but you'd be restricting the max airflow? What happend if you have too big of a carb on a stock engine?
it won't run very well down low. having too large of a carburetor will kill low speed air velocity which is what builds torque. that being said i had a 36mm mikuni on my stock motor that just has an FMF pipe and through the midrange it ripped like crazy...but it was pretty lazy on the bottom end
most guys say that the throttle response is much better. and should give you more power up top. hopefully someone who's done a definite before/after on it and they can chime in