Hi guys
I want to clean up my catalytic converter and oxygen sensors
What is the best way to do it

There's no real good way to clean them. Normally you just change the upstream sensors, it's not that they get dirty, they just get lazy and don't switch as quickly as they did when they were new.

Converters clean themselves for the most part, and when they can't any longer they're toast.

You would get a cat efficiency code or a flashing CEL if there was an extreme temperature variance.

Replace all four sensors as a maintenance item. They don't last forever. You and your mechanic need to make the decision on the catalysts.