Sounds like it could be the choke. Observe the choke plate on top of the carb - when the car is fully warm the plate should be completely vertical. If it's not, then the car will still be riding on the fast-idle cam and won't come down until it's properly open. The choke pull-off could also be malfunctioning (it opens the choke slightly as soon as the car starts up).
As the engine warms up, the bi-metal coil inside the electric choke cap opens the choke, and a stomp or two on the gas pedal will have it idle down. If it's an electrically heated choke make sure you have voltage at it. Some electrically heated coils also have supplemental heat coming from a tube that goes to the exhaust or from coolant (usually stock though and not an aftermarket Edelbrock). In your case it's most likely just an electric choke cap -- check that it has voltage, and that the choke opens as the car warms up.
Personally I'm not a fan of electric chokes. They seem to work o.k. in areas with mild weather, in my part of the U.S. it can be 10 below one day and 60 degrees the next. So that made it an exercise of constantly adjusting the choke cap -- not enough and it wouldn't start on a cold day, too much and it never idles down and wastes a bunch of gas (fouling the plugs while it's at it). Electric chokes imho were a lame attempt at automation before EFI, much like the ton of other vacuum-operated solenoids and valves throughout the car cluttering it up and making it unreliable.
I much prefer an old-fashioned manual choke. You control if / when it opens or closes, and you always know where it sits. Pull it out until it starts up, push it in a little, tap the gas, and close it up once it keeps running without stalling. You can still get the cable / conversion kit for about $20.