I just put in a new stock replacement electronic distributor on my 383 in my 70 dodge truck that already had electronic ignition. The shaft was very sloppy on the old unit and was causing it to ping under load no matter what I would set it at timing wise. I put in the new unit, timed it in. It idles great, and runs great at higher RPM's. The thing is at above idle and cruise RPM, it backfires through the carb, and makes popping noises out of the exhaust. It bucks and pops, but does not die, like it is breaking up somehow in the mid RPM range. I only changed the distributor, so this is the only variable. Any advice? thanks!