Since the start of the new STAR Smog Check Program smog station owners and smog technicians are being EXTRA careful to make sure vehicles are equipped with correct catalytic converters.
The smog check technician will check the catalytic converters EO numbers. If they don't match the required CAT EO numbers for your car it will fail the visual portion of the smog check as an emissions tamper.
Below is the link to the Air Resource Boards Aftermarket Emission Parts Lookup. Use it to check if your Chevy Metro's CAT is in fact not for use on your car.
http://www.arb.ca.gov/msprog/aftermkt/devices/amquery.php
