...Ranger when its very cold outside? When I start my truck in the morning or after it sits for a period of time, i have to give it gas and leave my foot on the gas for a few minutes (sometimes longer depending on temperature) If I let off the gas when first started, the truck stalls out. after a while if i let off, it bogs right down and growls, then jumps up to 1500 to 2000 rpms and again and again until i control with my foot again. Any help would be greatly appreciated

This is normal on most new fuel injected vehicles,It is similar
to choking the engine,even on all new peterbilt big rigs.

I had the same problem, its a sign of a dirty O2 sensor. They are not that expensive, but they have a good deal of control over the fuel/air mixture and can effect mileage greatly in the winter.