This isnt that difficult. The bung should still be in the pipe. With downstream sensor still in the bung. remove sensor. Open package and drill the center of the non fouler so oxygen sensor will fit. Now drill the second one.
screw them together and install into bung where original downstream sensor was. Install sensor. Clear codes.
Now sensor should function like the catalytic convertor is still intact. or, dont bother with it at all, as downstream sensor is an emissions monitor,and does not contribute to performance. Black tape to cover the light.
