I have a 78 vette that has a misfire problem when it warms up. I have changed the wires, plugs, cap, coil and rotor. EGR valve, that needed it, mufflers and converter, needed them too, rebuilt the carb, checked the timing and tried to advance and retard it, thermostat, and checked for vaccuum leaks, none found. A shop I tried said I did everything right. It could be a bad throttle base on the carb. I ordered a rebuilt carb, same results. After it is warn when I am at idle at a light, I can see my tach drop out briefly and feel it too. Then I sputter on acceleration till at a constant speed. The engine has about 10,000 miles on it. It's dirving me CRAZY!...Joe