[Gaz64]

Jon,

The phenomenon you have mentioned, referred to as "reversion" or "standoff" should generally only happen at wide throttle openings and higher rpm.

Your engine is certainly capable of being happy with Webers, and not as wild as some I've seen, including my cars.

Have you synchronized the carbs correctly?

Have you measured the manifold vacuum at idle?

How much timing do run at idle?

Have you used a wideband O2 sensor to measure your Air/fuel ratio?

70F10 seems a bit fat for a 306, how far out are your mixture screws at idle?