Dave,
It looks like, unintentionally, you have introduced confusion into the discussion with your statement in post #31, 'smallest diameter of the bore venturi'.
The bore [ throttle bore ] is different to the venturi, & is located below the venturi on downdraft carbs. The diameter of both is also different, creating different pressures.
I think you also misunderstood or misread what Kenth said about the PVA port being below the t/blades; he said this is the case during acceleration, when the t/blades are opened for power. At idle, the PVA port is above the t/blades & I think we are all in agreement about that.
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