1991 D250 Runs poorly after 10 minutes running. on 1991 Dodge D250

Truck misses very badly 10 mins after starting, wont start again very easily, until cold again, then will run perfect for 10 mins until engine warms up, changed cap, rotor,plugs, coil is good, any suggestions read about a coolant temperature sensor, ?

Asked by for the 1991 Dodge D250
could have a map sensor problem scan test for codes
this motor was replaced with a multiport fuel injected motor, (1995-2001) not sure where to find plugin to scan codes,not looking like there is one below dash anywhere, a mechanic told me some kind of sensor in the distributer could be bad,after you shut off motor, but leave key in on position, you can hear fuel still shooting to injectors and the fuel press regulator on fuel rail
plug in should be under the dash or on the firewall under the hood