Do I need to replace my catalytic converter?

Do I need to replace my catalytic converter?
Added (1). I've got a 2001 Honda CRV w/ ~185,000K on it. Heard a rattling sound and had loss of acceleration power. I took it to a mechanic and he said that I needed to replace the catalytic converter or it would get clogged and could blast out a valve. Also, exhaust system has rust so he says he needs to replace the whole thing from the cat back… Please advise.

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