1995 Dodge Ram backfires horrible only when cold

Need help when is engine cold start 12 or more hours vehicle will run like it`s jumped timehave replaced coolant sensor replaced computer with new parts has extremely long injector pulse width 30ms floods engine gas mixed in oil if you put trans in reverse it will idle somewhat and only in reverse have checked the wiring from coolant sensor air temp sensor map sensor from each sensor to computer no problems found has no open wires all connections appear good on scan tool at cold start if outside air temp is 40 degrees coolant sensor and air temp read 40 degrees if you can keep engine running long enough to reach 185 degrees engine will run good my question is what is responsible to let in injector pulse for this long oh forgot also has new crank sensor and pickup coil and I have indexed the dist. Also this problem showed up out of nowhere any help is appreciated