I've run with the CEL on with other cars and didn't care, but this car turns off the cruise control when the CEL is on
so it has to be off (if I have to manually turn it off occasionally with Torque Pro that's ok but not every day).
I'm thinking of keeping the first o2 sensor in place. I'll plug my wideband a/f gauge into the existing second bung and have a bung welded into place AFTER the secondary cat and plug the second cat into the new bung. The order would be unchanged, just the placement of the second o2 sensor would change.