do you have enough free play in the throttle cable after you replaced it?
if so, i'd say that is sounds like a vacuum leak. hold a lit cigarette around the carb/intake area to see if there's any air leakin out. or just start the bike and spray the area w/ carb cleaner and listen for a change in the revs.
i highly doubt that it would be your main jet or needle position as those are only active in the 1/3 through full throttle range. sounds like your problem would be the pilot jet/air screw if it's indeed a carb issue.