Stalling and backfiring?

My truck is stalling and backfiring while driving down the road. It will shut off and coast a little bit and turn back on. It jumps and backfires. This is more frequent in the a.M. But will in the afternoon when I get out of work and it has sat and cooled off for approx. 8hrs. I have code P0443. I have changed out the ignition coil, crankshaft position sensor, Idle Air Control valve, purge control solenoid valve, distributor cap and rotor, MAP sensor, gas cap, and spark plugs. Some times she runs perfect and like yesterday after work she shut off about 12 times. Idles ok but put it in gear and try to move. After she warms up then she runs better. Sometimes at the light she will idle good and then just shut off. I am stumped on this. Like I said sometimes she runs good and sometimes she doesn't.