340 fuel/ignition issue?

Midnight,
The base gasket [ if incorrect ] usually causes a problem with sec operation. It will affect AV dashpot operation. If secs are working ok now, that is good, gasket ok.

Make sure you have the correct air horn gasket. There were at least two types, difference was the divider between the pri & sec section of of the gasket.

Rich idle. Are the little pods under the pri jets sealed properly to the black body? Leaking here will cause richness. Are the T-slots correct: 0.040" or less below the blades. The TQ has 3 air bleeds for the idle system, various names used for them, but they bleed air into the idle fuel. Make sure none are blocked. Only other thing I can think of is corrosion of the alum. If this carb has corrosion inside the alum & the corrosion is blocking passages, it might cause strange problems like you are having.

Another thing you could try: you have a smaller 800 TQ, correct that works ok? As a last resort, use the 800 air horn on the 6322 body.