im still wondering about the intake manifold causing this problem.It almost seems like it will leake then something will block the leak for a second then leak again.the dist is good im sure of it.it has i high perf kit in it and im pretty good with timing.i dont use a light but i play it by ear.i set it by wot untill the popping goes away and set for max advance at idle untill runs the smothest for i use no vacc advance.it acts like the metering rods are moving up and down slowly but when i look in to the carb i hace no fuel comming form the to so that tells me the rods are all the way down.its kinda a stumper to me.Think i should pull the manifold and reset for a vacc leak?or look elswhere?thanks