1992 Dodge Dakota ignition cuts out, causing backfire, pingin

I have a 1992 dakota 3.9L, 4x4
when cold very hard to start( cranks good ) When finally getting it started I must let it warm up or it cuts out like timing jumps out of wack. Can shut off and restart runs fine until it cuts out again which is happining quite often. No engine codes are coming up and have already replaced engine computer, distributor, map sensor, tps, ign. Coil, crank sensor, ign. Module. Can't think of anything else to change or look at.