exhaust smoke while sitting at stop light

[Powerstroke Man 6.4]

ok little update, im thinking its fuel related. after the truck is warm the fuel rail pressure on the ai is showing 31808 and is stuck there with little revs its drops a little but not every time down around 4500 for a split sec then it goes right back too 31808 what may be the cause of this. while the truck was running put up on the h&s icp and it was 3.9 and it was steady with throttle and worked as it should but the ai would show 31808 at idle any help would be greatfull thanks allen

I think that 31000 number is a AE problem my buddies tuned 12 used to say that at idle then when you tap the pedal it will drop to the "right" psi for a second then it will go back to 31,000.