is it necessary to recalibrate ECU after replace catalytic converter?

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i recently purchased for my wife a used 2003 4-cyl Camry, a/t, 125000 miles, from a toyota dealer. Nice car. After a couple weeks, the check-engine light came on. I got out my Actron OBD II code scanner, which i used to retrieve a P0420 DTC. I researched that DTC on the internet and found out it is a "catalytic converter not performing to spec" issue. I erased the code, and it has not returned in the month since then. I dropped by the toyota dealer to discuss the issue w/ a service tech, who told me that altho i could replace the catalytic converter myself, i would still need to bring it by to them so that they can "recalibrate the computer" after the new catalytic converter has been installed. Back in the 60s and 70s, i had A LOT of experience working on VW Bugs, rebuilding Bug engines, even once rebuilt a VW bug standard transmission. So i like to think i know a little bit about auto mechanics. But back then, VW Bugs did not have catalytic converters, much less onboard computers. So i need to know: on MODERN cars, do you need to recalibrate the onboard computer whenever you replace the catalytic converter? or is this something particular to Toyotas? I have both the Chilton AND the Haynes shop manuals for this car, and neither one of them mentions any such requirement. One further note: I found a TSB for this car on the internet, Toyota TSB EG024-04, relative the onboard computer and P0420 DTCs, but the tech at the dealar told me it does not apply to *my* engine b/c it was built after the Production Change Effective VIN (and that jives w/ what i concluded).