1991 1 dodge Dakota 4 cl won't start when it's cold out but after the weathers warms up its fine. I replaced the fuel filter but don't believe that was the problem

Fuel Filter -- doesn't know or care about the temperature

Are the Spark Plugs in the motor over 3 years?

Thermostat -how old is that ?

Oxygen Sensor --over 100,000 miles,replace it

Plug Wires? How old? & dist cap

What your saying-- is when cold-- it is in open loop & won't
run until warm & in closed loop.there is some clue to what
to diagnose

Are all the vacuum hoses on according to the diagram
under the hood ?

What is the fuel pressure at the schrader valve on motor,
with & without the vacuum hose on pressure regulator?

Is the battery any good-test it