Avanti has original 289 and AFB with an Edelbrock electric choke and a Pertronix billet distributor, heat riser removed. Twice after going to a cruise-in after the car has set for a couple of hours, the engine will restart readily and then begin to stumble and die. Then it's really difficult to restart. (usually accomplished by manually holding choke plate closed and flooring accelerator pedal.) Once back on the road, the stumbling stops and it runs well -plenty of power acceleration and idles well at stops. The car usually cold starts well but has caused the same problem at times even on a cold start. I'm no mechanic and am clueless as to how to resolve this problem. Any ideas would be appreciated.