Idle problem

A PCV valve will cause to happen what you have. It is leaning out and struggling to stay lit. If it is not the PVC valve, look for a vacuum leak somewhere else! That 3310 is an excellent carb. If you take the curb idle screws out 2-full turns, it should be sufficient idle fuel. If you have to turn the idle screw up to make idle a thousand rpm or more, too much of the idle transfer slot is being uncovered and then the high speed system tries to come into play. You'll see fuel dripping from the boosters or at least weeping fuel. Idle vacuum should not be 10 with the car in gear...a sure indication of a vacuum leak. Disconnect the PCV valve and plug the carb nipple and see what it does. If the power valve were the culprit, it would run overly rich and you would smell it. Those carbs have a 6.5 powervalve that does not open until vacuum drops below 6.5 inches of water. Your engine is smoothing out when you hit the throttle because it is getting the fuel/air ratio it needs to operate as it should. I am glad to see you have a vacuum gauge! I wouldn't be without one on my cars. Low vacuum also shows late timing. I'll bet the engine tries to run on when you shut it off too....right? Find that vacuum leak!
Pat