Backfire on deceleration?

@vegasanthony did you ever resolve this issue? I just fixed mine. TL/DR: it was the EFI tune.

I put in the 46rh so now my revs are super low on deceleration, but that didn't fix it. There was less popping because less engine deceleration, but it was still there.

The 46rh was using pressure switches to control the OD and lockup functions. It was working fine, but doesn't allow for kickdown out of 4th or lockup so I would have to flick the rocker switch if I wanted that. I could have installed vacuum switches to do it automatically when the vacuum drops, but why would I do that when I'm already running the factory PCM?

I know the transmission would need a vehicle speed sensor to make it work, but that would do away with my cable driven speedo since the Magnums were electronic speedos. I was prepared to give up my speedo but then I saw on FABO a Magnum EFI expert mention you can use a speed sensor from a late 80s Ramcharger and still use the cable speedo (shout out to @magnummopar).

Bottom line, I installed the speed sensor, wired it all up, and now I have zero after firing on deceleration (plus PCM controlled OD and LU, which was the whole point of the work). So I guess the PCM needs to know the car is moving before it will cut the fuel on engine deceleration.