Put em one in front of the other just downstream of the y? You kinda loose the distinction for the ecu to recognize if one bank has gone off the other, but if your injectors are good and the harness is good, you likely don’t have much variance between banks...I have to think that being so close to the dump is giving a false rich return... theoretically, you could put one sensor in and pair the output wires to go back to the ecu and trick it into thinking there are 2 sensors. It won’t care if both sensors return the same values, and as long at the mechanical and electrical end of the injection is good, it won’t either...