340 fuel/ignition issue?

Midnight,
[1] Gasket in post #8. there some differences there & from memory if it is wrong, it can cause an air leak to the AV dashpot vacuum passage. If you hold the black plastic body upside, you will bee a recess/groove that follows the curvature of the secondary bore; this at the rear of the sec opening, passenger side. It connects with a passage in the alum base plate. That passage has a small hole in it that is drilled into the sec throttle bore. When the sec blades are closed, this hole is covered; so you have to open the sec blades to see the hole. Trace this hole/passage/recess back to the gasket & make sure that nothing is exposed because the gasket is wrong.
[2] The base gkt I was referring to in post 5 is the one between the carb & manifold. The passage referred to above can be uncovered with some TQs