white exhaust while in reverse

i have a 2001 dodge ram 1500. i just replaced the radiator yesterday, and i have a misfire in the first and, 6th cylinder. i drove it a total of 30-50 minutes yesterday after the radiator was replaced. as i parked for the night i reversed in and i noticed that there was white smoke coming from the exhaust. i decided to let it rest till morning. i fired it up this morning and it seemed ok drove it to autozone and it engine light red misfire in cylinder 1 & 6 nothing else i drove it home and the heat gauge whet high not redline, not even the last white line but pretty high. no white smoke came out untill i put it in reverse. the smoke smelt like burning gas the work that has been done to the truck is: new engine new spark plugs wires and coils new oil pump new thermostat new fuel pump new radiator new tires the a/c and heat don't work but the last week i have left the knob on the max heat, not sure if it is a contributing factor but im giving all the info i can please let me know what you think