No-load Misfire Puzzle

If it is surging at light throttle openings cruising down the road it is running lean.....make sure you don't have any vacuum leaks. Spray a can of carb cleaner around the base of the carb and the intake manifold. If you have a vacuum leak the cleaner will get sucked in the the rpm will change..I had the same issue and the carb base gasket was blown out about 1/4 inch. I just rebuilt my Edelbrock carb with a kit from Summit, piece of cake.