"Since the problem is only on one side of the engine, try putting the left O2 sensors on the right and the right ones on the left. If the code stays on the same side, the problem is not the sensors. If the code moves with the sensors, it's them. Then, if that's the problem, I'd try swapping just the sensors in front of the cats and seeing what happens to the code. If it moves, the problem is the front sensor. If it stays put, it's the rear."
Good idea to swap the sensors from side to side, we did that and when we did it said the same side was at low efficiency, that is why we put in a new cat on that side, but we are still getting the same error code.
I think Jim's idea about the height and spacing of the oxygen sensors is where the problem actually is.
Ed
