Is it possible to clear the catalytic converters out and not replace?

I drive a 2002 Camry. Since I’ve had it it’s had the check engine light on running a code MAYBE P0420. Also maybe something about gas cap… it’s been a minute since I’ve scanned it.

My FIL said something about the cats clogged and to keep running RXP through it. I trust him wholeheartedly, he’s a fantastic mechanic. Just wondering if anyone else has had this problem.

In my county we’re now required to get emissions tests, and I know if I have to replace the cats then Id just rather find a new car. Just sucks because that is literally the only problem with this Toyota. Everything else about it is perfect, it’s never left me stranded or anything. It’s still fully functional now, I just know if I can’t get it legal it’ll be time for a new one :(.