I see you are still on line where r you from?

 

I would still check the two jets as I described just to be sure , as compressed air dosent always do the job (I have seen exactly what you describe so many times due to these .)
Air leak would give similar effects but on two cylinders? not as common.
P.S. touch a wet cloth on the headers and listen for hissing (saves burning your hands ....ouch)

 

Check the idle (low speed) jets if manifold isn't getting hot. Most bikes have the high rev jets kick in from 3000 - 4000 rpms. So if you completely let off while at high speed you would get a stumble if the low jets were goofing on ya. Sounds like you got everything pretty much under control though. Only suggestion that I could add would be to have it dyno'd with an a/f monitor -- that would let you know beyond any doubt if it it your high or low speed circuit but wouldn't tell you which cylinder. But even at idle the manifold should heat up to untouchableness within 15-20 secs.