I'd try hooking up a manual fuel pressure gauge, manual vacuum gauge to the intake and drive it. And after checking those readings, move the vacuum gauge to distributor vacuum advance line and see what is happenning there when driving. If you're not sure what the gauges should be reading, then I'm sure that the info is in a GM service manual. Also, I tried 'rebuilding' my original 1 barrel carb and I discovered, after I took the carb to carb only guy, that installing a carb kit is not actually rebuilding it. After installing the same carb that was repaired by the carb guy, my float angle was well out of whack, it worked perfect.
