Draw vacuum from CID determines how fast the fuel is drained from the float bowls, fuel pressure out the pump determines how fast the bowls fill back up and replentish the supply.
With alc the volume of fuel available in the carb is cut in half (2.1 times the volume to create the same BTU's as gas) so the trick is to increase the fuel pressure (which is fuel delivery speed) the downside is the needle and seat also bowl volume. More pressure and the N&S get over-wellmed, Too little and the bowl drains and the N&S cant keep up.
I modify Weber IDA carbs and extend the bowl volume by 150% because the N&S can only handle 1.5# of fuel pressure, and the total volume of the bowl minus the space taken up by the float, the transer of fuel the engine takes is more than the fuel is replaced by the pump because of the N&S
My assumption is that the alc carbs were for designed for roundy round cars and getting on an of the throttle kept volume issues at bay because they were not held wide open for a 1/4 mile.
Not knowing exactly what you have, how you run it or any of the problems you are having, Most issues can be handled by extending the bowls to increase available volume to the engine to complete the full pass on alcohol
