If you have a 2001 “California emission” system in your vehicle, doesn’t the quality of gas in other states cause the O2 sensors to trigger a failure in the converter when there is not a failure? Aren’t the converters set for the less polluting California gas required in that state?
Most manufacturer’s now make vehicles, parts for them, and fuel for all 50 states. California isn’t special anymore. As for your vehicle specifically, since you didn’t bother to tell us what is was, no idea.
If you have a California car, you can still buy a California catalytic converter for your car in other states.
What makes you think the gasoline is any different in California?? Don’t change the converter, change the o2 sensor, which I bet is the same for all states…