Sounds weird, basically cylinders 1,2 & 3 are your bank 1 And 4,5 & 6 are bank 2, so can understand the O2 sensor on bank 1 Picking up a fault if you have a miss on 1 & 3, but bank 2 readings should be ok Sensor 2 is just a reading sensor as sensor 1 on each bank is the signal sensor. Guess if uve done the plugs and coils, and you're getting a spark through the plugs And no air leaks, ull need to compression test the cylinders and check the fueling side ie injectors