[Governor Dinwiddie]

Unfortunately there are O2 sensors fore and aft of the converter. Unless you can fool the automobile's computer somehow, your air/fuel mixture will be messed up.

[nascarnation]

The upstream sensor(s) are the ones that feedback to the computer to adjust the fuel injection.

The downstream sensors just make sure the cat(s) are working properly.

If you don’t have state inspection/testing, you can eliminate the cat(s) if you don’t mind the “check engine” light on all the time (P0420 codes).