There are two idle mixture screws on your carb. ( On the front of the carb, not the screw on the linkage arm that sets your idle speed) Turning them in leans out the mixture, and out makes it richer. If your car (all warmed up) is at idle, and you turn either one or both screws in, and it stalls out, then you're on the idle circuit. If the screws have no affect on the idle, then you're not idling on the idle circuit. If that's the case, get back in here and let us know what's happening.