Most states now give an instant fail if downstream O2s are turned off. They started here in Arizona a couple years back. They mark your vehicle as "tampered", you have to go to a special station where they know their shit. They even cross reference PCM checksum with manufacturer - so at that point a simple tune will fail even with cats and downstream O2 activated. They also proceed to inspect your exhaust to ensure it's OEM and have all your other emissions components installed.
Anyone in Arizona, don't get flagged with "tamper", they throw the book at you. We've become California.