2008 Chevrolet Silverado P0174, P0300

Truck was dropped off with check engine light concern. Pulled codes and found all cylinders mis-firing one time or another. Replaced plugs with ac delco, cleared codes and test drove. Engine light came on after it started to flash while going down the road, and the traction control light also on. After light stops flashing the traction control light goes out and check engine stays on. Code p0174, p0300 are stored in pcm. Misfire counter never sees a misfire. With a lean code on only one bank I swapped upstream O2 sensor from bank to bank and code still comes back with bank 2 lean. Any help would be great. Thanks