I got a 2017 Jeep Patriot 160k miles ( mainly highway) Past year I was dealing with a p0420 code “Catalyst System below efficient threshold bank 1”

I took it to a shop for diagnosis to get a second opinion and they weren’t to much help all they’d said was “ everything was working fine “ ( i was hoping they would give me more info like the pre and post cat temps.

I replaced my O2 sensors with OEM and the code is still there. I’m rooting down to the catalytic converter, I did have a valve cover and spark plug tube seal leak (FIXED) which could have contributed to a failing cat.

I looked inside my cat and I the honeycombs were clean, but maybe it could be clogged internally or the other side.

Anybody got inside on a failing cat or best way to inspect or would it mainly be just the cat. I like my car and will replace if need be just want some other answers.