also anything done to the carbs? stg 1 or 7 or stock? sounds like sync is off a little and lean. try also turning a/f screws a little out, what are they set too now? did this just start happening?
someone else prob has a better clue as to what it is but just some basic starting points for ya.
I just synced the carbs. It is running pretty rich at idle. It has been running bout 3 mins with the choke off. i dont have any idea what is in the carbs. Its exactly like i got it. but the air screws are 3 to 3.25 turns out.
does it still idle funny after a romp around time? at what rpm do you have the idle at? hmmm...3 to 3.5 turns isn't stock, but you do have a kerker--maybe they need to be set like that b/c of the exhaust. hmmm. have you tried "sea foam" or "start your engines"? couldn't hurt. also consider "shotgun" or "pea shooter", couldn't hurt neither.
float height out of adjustment, jets/mixture screws, but doesnt sound like you have been playing with those lately so float height might need to be checked