Just fought this problem on one... Try swapping the pre-cat o2 sensors. Turns out on mine, the fuel trim on bank 2 would go down to -25%, indicating a rich condition on bank and shutting off bank 2 injectors. Turns out the o2 sensor was providing false readings. This false rich reading also indicated the air injection system was not functioning properly.. When ou swap the sensors, monitor short term fuel trim and misfire data and see if the problem moves to other bank. Easy test and easy repair.