I am having some trouble with my 99 Xj600N
Symptoms are rough sounding idle, hanging revs at idle when warm - sticks at 2-3k at traffic lights for 10 seconds, then drops back down to 1.3k idle. Pulls fine throughout all the rest of the throttle range as far as I can tell.
Putting on sync gauge, no2 cylinder is stuck pulling huge vaccum, all other cylinders respond to adjustment, no 2 shoots up and will not move.

Also noted, putting my finger over these holes on 1,3,4 carbs kills the mixture, covering these holes on no2 (problem cylinder) makes no difference.

Any smoking guns to check first? Ive pulled the carbs twice and been through them, I cant find anything obvious, all air passages I can blow compressed air through etc, Pilot is spotless. I could not find any tears in intake boots either. Mixture screws are still blanked off from factory, spark plugs show similar mixture across all 4.
As I understand it, No2 is the master carb, should I just adjust everything up towards that? or should it not be roughly pulling the same vacuum as others when idling?
Cheers!