Toyota Repair: P0420, exhaust leaks, cat converter

Question
Ted
I just purchased a 2000 camry CE
it has 142k on it
I don't know for sure if the o2 AF/AV sensors have been changed but tfrom what I see the harness wires seem new
can you tell me if my car falls under the TSB?
also what exactly is a TSB? I am not clear if it means there is an issue with certain vehicles and the outlined procedures are to correct them at a cost to the owner or are the dealers obliged to correct them without cost (LOL)
any help at all is appreciated
I know first I need to check for exhaust leaks, then o2 sensors then cat
also I am in california, just passed testing, I don't understand although the cel is not on, the code is still there,,   but if the cat is finished/needs to be replaced, how can it pass testing?
trust me I have looked at loads of discussions on this but unfortunatley i never seem to see any resolutions

I just cleaned iac, it was idling high 2,000 rpm and cleaned egr, and TB

vin  4T1BG22K0YU933251

IF THE ECU IS Supposed to be flashed, and it has been will the dealer know?  there is no sticker on the hood, but I believe the hood is not original( no stickers at all on it no vin and there are shocks, not a prop up pole like other camry's I have seen, I think the hood came off a solara, is this right?
car I don't know if the car was originally meant for CA, other than a sticker on the hood, is there a way to tell or does it matter?

Thanks so much

Liam

Answer
There is no service bulletin available for this model year camry with this VIN#, the cat converter should be replaced, it has two converters, one directly on the exhaust manifold and one further back, only the one attached to the manifold needs to be replaced.