2000 Tahoe, 5.3l, 4wd 198,000 miles.
I am having an issue that I can't figure out nor can I seem to find exactly the right direction to go, or I'm missing something logically. Cold start she's fine, idles reasonable and drives fine. When I go somewhere, store or work, I start her and she seems fine but i put it gear and start going and she misfires and runs rough and doesn't want to go. It varies is severity, especially after I replace something when she'll run fine just long enough to make me think I fixed the problem. Most of the time I can give the throttle a good rev and then it's either fine or fine enough to get home. One time I could barely get going and it was shaking. Drove to another parking lot and turned her off and checked codes. Started her up and she was really rough, held it at 2-3,000 rpms and after a minute started to idle fine. Wife said it was like something was clogged and that pushed it through. Ran fine on the way home. Usually this is after coming out of the store so not hot but not cold. When it started I did get a misfire code, first on cylinder 6 then while troubleshooting just random misfire code.

Swapped wires, plugs, coils around didn't change. Put new coils, plugs, and wires on ran stronger then she has in a while. But the aforementioned problem was still there. Checked fuel pressure key on engine off was at 48 psi. when pulling the vacuum line of the fpr went up. put a new fuel pump in, filter, cleaned the tank, blew out the fuel lines with alcohol, cleaned the injectors. I hear each injector opening and closing when I put a screwdriver to them. Can't see any cracks in the vacuum lines, Did the spay carburetor cleaner around the heads and intake to see if the idle changes to show a gasket or such, idle did not change. Since finishing up the fuel pump I've drove it three times, about 50'ish miles each time 25-30 to town and back. First and second times no problems. Last night went into town picked up food and she was fine, went to get another store and she did the hesitation idle problem when pulling out of the parking space. Put it in neutral and revved it smooth. Drove fine on the way home as I wished I had more beer to drown my sorrows in. The common thing is that it does it when I am leaving the parking spot at a store. Doesn't do it on cold start. Doesn't always do it when leaving every parking spot( Like last night didn't do it leaving the taco place(first stop) but did it leaving the grocery store(second stop). Runs fine on the highway,

What am I missing looking at?