My '65 D200 developed a problem while cruising a while back. There is a loud "popping" in the exhaust, especially when the engine is slowing down, but also periodically while cruising. I've run a vacuum check (all o, a compression check (all cylinders but 1 reading 125 psi, with the 1 low 1 reading 115 psi, but it's still within specs), the plug wires are showing consistent resistance. Since it started, I've changed the fuel filter, rebuilt the carb, adjusted the valve lash (most were withing a couple thousandths), checked the timing and dwell (all o. I pulled the plug wires one by one and at an idle, the engine rpm dropped with each disconnect. The engine has a MOPAR electronic ignition with an orange ECU that has been performing flawlessly for 12+ years. My ears tell me there is unburned fuel getting into the exhaust that is being ignited in the exhaust manifold or pipe.

Could this be a problem be with the electronic ignition ECU? If so, can it be checked or should I just buy a new one? Can I check the primary voltage going to the coil? What should it be? I'm out of ideas and all suggestions will be appreciated.