03 K1500 PO300 Woes

[JJMiller]

2003 K1500 Suburban 5.3 L Flex fuel
I went to my Chevy dealer to have the knock in the steering column that was recalled rectified. Works great so far. Later that day the truck starts misfiring. OBDII code PO300 (Random Cylinder Misfire) cyl 1,3,5,7. When i shut the truck off it resets and no misfire. Then I figured out how to make it come back, I would hit the accelerator downshifting the tranny and bam misfire. Took it to the mechanic and showed him how it happens and now it wont reset but it is only cyl 1 now.

What has been done so far!

Disconnected altenator and it runs fine, ordered new one (145 amp?) still #1 misfire
changed plugs, 1,3,5,7 all black 2,4,6,8 all lean
changed wires
swapped 1 & 3 injectors with 2 & 4. #1 still failing
swapped coil packs from 1 & 3 with 2 & 4, #1 still failing
Fuel pressure test shows normal
Smoked engine and no leaks but changed intake manifold gaskets anyway.
Changed O2 sensor, Black as the plugs. but the electric shows 1.1 at shut down
Jumped wire from computor to injector directly still misfire
Cats are ok and no valve ticking at all
I even rubbed a budda belly and it still showed misfire.

I am at my wits end and need help, Please respond!

JJ