Carburaror (again)

1948 Pontiac Carter 2brl. Professionally rebuilt 12 years ago, driven 2000 miles and unused since. Idles nicely. Severe hesitation (stall) if pedal slightly depressed. All s peeds. Only way to pull away in an intersection is to stomp on the gas. R eplaced accelerator pump, no change. Swapped with 1952 Pontiac carb and al l OK, telling me that vacuum advance and electronics is fine. My amateur opinion is that stepping on the gas introduces an inordinate amo unt of air. All advice appreciated. Not a lot of carb repair people left. I'm in the Po rtland, OR vicinity. Thanks, Ivan Vegvary