possibly you have crud in your fuel system and it is clogging the idle circuit, make sure you run an in-line fuel filter right before the carby. To see if it is a clogged idle circuit, take the air cleaner assy. off and run the engine, rev it up good and proper, then clamp one hand over the carby at the same time as opening the throttle to full. The car will want to stall instantly and it will suck your hand to the top of the carby, but the immense vacuum created in the carby should suck any small restrictions through. Take you hand away just before it stalls and if you like, do this whole thing several times. If the idle comes smooth, then crud in fuel was problem, if it doesn't perhaps start looking for vacuum leak at hoses or manifold, as this could also cause the symptoms you describe.