If it never ran right and there are no other clues, yeah .. check the exhaust .. That big bolt in the right side of the muffler (behind the heat shield) gives access to a tiny baffle tube.. the tube is the first thing to get packed with carbon. All exhaust must pass through that tube. Poke a screwdriver in there.
check everything related to air intake. The bikes are sensitive to too much or too little air intake.
Since the carb was plugged up, surely cleaning the carb made some difference? If not, it's likely there's something else going on unrelated to carburation.. (be SURE its clean.. i have screwed up a carb-cleaning job more than once)
ignition seems ok since it starts and idles, but ignition misfires can be mistaken for fuel mixture troubles.
Check compression.. torque the head bolts ..
I really think it's carburation but it could be many other things.. there's no easy way to diagnose from a distance.. gotta get down and check everything until you find something.