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It really sounds like you're running extremely lean when your primary butterflies are moving past their fuel transition slots in the venturies, sucking air instead of fuel. You could be compensating for excessive fuel pressure by cranking down on your float bowl float adjustments to compensate for the fuel pressure over-powering the float needle valves?? What's your fuel pressure?

Try one thing.. Mark where your carb bowl fuel level adjuster nuts are at now. Raise the bowl level by turning the adjuster nuts 180 degrees counter clockwise, effectively raising bowl fuel levels. Immediately go take a test drive after you made sure fuel isn't pouring out of your bowl vents. See if that impacts your drivability. If it doesn't at all return your fuel levels to the original "marked" setting. If it does make it run better take a look at your fuel pressure, re-evaluate your bowl level adjustment procedures and fine tune your new fuel levels.