Carb problems

I recently bought a 1964 Barracuda with automatic and a 273 engine. On shut off the carb is steaming (boiling) . It is a 2 barrel Carter and I recently had it rebuilt. The choke is a well type Carter and I notice that the engine paint is all burned off on the manifold around the choke. The car runs well but gets poor mileage. Obviously it burns too much gas but it was rebuilt by a professional so I'm reluctant to fiddle with it. The other thing is that when I stop at a light the engine does not return completely to idle and it races unless I lightly tap the pedal. This also happens while driving-if I take my foot off the gas the cars still keeps on going and will maintain 40 mph unless I tap the pedal. Any ideas? Thanks Ken