1998 K2500 Missing and Backfiring - HELP

I'm driving a 1998 2500HD, 4x4, 4L80E, 5.7L. This morning on the way to work it started hesitating / stumbling under light acceleration, then a few stumbles at an idle, then consistently stumbling under acceleration, and even starting to have the sounds of a very light backfire. I'm not sure if this would be considered an intake backfire or not?

The fuel pump was changed about 15,000 miles ago, the fuel filter about 30,000 miles ago, spark plugs about 30,000 miles ago, and everything has been meticulously maintained. I feel like it is fuel related, possibly injectors?

Now, at the end of the day, the problems are more pronounced, the missing, light white smoke coming from the exhaust, and will not start after warming up and shutting off. When cranking, it is not a normal speed crank, but slow and painful.

Thanks in advance for your thoughts.

If you have a check engine light on get that checked out. That will give you a place to start. After my truck sat for about a week in the rain it started hard one morning and missed and backfired all the way to work. Did some checking with the scan tool and pretty quickly determined it to be the dist. cap. I think some moisture got in there. Anyway, hard misses are usually ignition related, the fuel systems on these trucks are pretty solid except for the pumps of course.