I decided to tune and sync my weber 40 idfs today for the first time. Everything went really smooth after reading about and watching video on the subject. First thing I did was check for vacuum leaks before going any further. After disconnecting the linkage and making all the adjustments, things seem to be running pretty smooth with the exception of the barrel for cylinder two will cough and burp. All four barrels are drawing 6 on my snail, with the engine warmed up. Any ideas what would cause this and possible corrections? Thanks in advance, this site has been extremely helpful to me in the past.

‘Spitting or coughing from the carb intake suggests it is too lean. Try opening up your idle mixture screw (turn counter clockwise}, 1/4 turn at a time.

All 4 Venturi read the same at idle?

yup

Turn the idle up with the dr side idle speed adj screw and remeasure. If your gauge has the holes in the base and body you might have to line the holes up to keep from pegging the gauge. Burp coming back thru the Venturi and at what rpm? I think of it as sneezing. Remember there are 3 factors. Idle jets, progression ports and the main jet circuitry.

maybe a blocked idle jet,not sure what your idle is but @ 900-950rpm my snail won't make much more than under 5 ,seem to remember balancing @ 4.5.
If you can't get a good result by using are bleed screws you most likely have a vacuum leak or uneven compression issue,when were the valves last reset for example and ignition refurbed ? ...no mention of engine size so have no idea from this point,good luck.