2003 Chevy Silverado

Engine Performance problem
2003 Chevy Silverado V8 Two Wheel Drive Automatic

Have a 03 chev c2500 with a 6.0L
Runs roough - have done all the basic tune up stuff
plugs, wires, fuel filter, O2 sensors.
Was still missing on bank 1 (driver side) and smelled of raw fuel at exhaust. Have good compression.
Sent it to a exhaust shop and had both cat's replaced. Replaced plugs again on bank 1 (gas fouled). Runs better but still misses.
Checked fuel pump for pressure and volume and it checks out with specs. Injectors are pulseing normal.
Checked intake for leaks, replaced maf sensor when it coded.
Even check ecm for bad ground.
What am I missing?
Help please