I have a check engine light for catalyst below efficency because the o2 sensor is bad. which 02 sensor is it pre or post cat and can it affect the performance of my car?

 

Cat inefficiency codes on any car I've seen have always been post-cat.

 

run the engine till its nice and hot then clear the code and see if it comes back, check the wiring to the O2 sensors ( the one closest to the cat ) but
P0442 generally the cat on its way out and you will notice the difference in performance