I have done an extensive search/experiments and kind of sure that it is my Right CAT that is at fault but before having it replaced I have one question.

My issue:
1. At first I got O2 Bank 2/Sensor 2 fault code.
2. After resetting and driving I got O2 Bank 2/Sensor2 and Sensor 1 fault codes. Reset it again and cleaned MAF sensor.
3. Got Misfire on 1, 2, and 3 Cylinders as well as as O2 Bank 2 both sensors under load. Decided to switch Coil #1 with Coil #4
4. The same, misfire on 1, 2, and 3 came right the way under load.

Without further due I concluded that it is my CAT 100%. Besides, it rootless when you gas it. It is a California car and emission is the key in here. The aftermarket CAT I was quoted costs $220 P+L that is not bad but not sure about quality.

Looking at the exhaust assembly I see multiple items:
1. CAT that sits between 2 O2 Sensors
2. Followed by a little resonator
3. Big resonator that combines both banks together.

Can someone please tell me if only CAT needs replacing or little resonator as well?

Thank you in advance.