Most likely this. Needs to be set so that at 60-70*F it is just barely
closed, almost no spring pressure on it. Then there has to be a 12v feed to the choke stat that is only "hot" when the key is in the run position, alterator field wire works well. This heats the choke stat when the engine is running, so that when you "blip" the throttle after some warm up time, the choke comes off. Set the fast idle on the second step of the cam, usually approximately 1100-1200 rpm when engine is warm. Once properly set, this will start like fuel injection.