Judging from the variety of codes, it might be just a sensor that went bad. But it could be a cat as well. Rather than guessing, I would pay for diagnostics and have it verified before proceeding with replacing anything.
The vehicle came from up north, so there was quite a bit of rust when I bought it.
The rear cat connects to the last section of the exhaust via studs and nuts. The studs are nubs now and there are no nuts anymore, which is causing a bad exhaust leak. However since this is at the end connection, after the cat, would it still cause this code?
any exhaust leak will affect you o2 readings, it will be in your best interest to get them fixed. i soaked the nuts in pb blaster and hammered a smaller socket on there, then used a battery impact to free them, it was ugly, but worked. these particular codes are likely from a bad downstream sensor on the rear bank (1). do not disconnect the neg cable bc your freeze data which set the code will all be erased. if you want to investigate you will need this info. when diagnosing engine problems with multiple codes GENERAL guidelines dictate working your way up from the bottom numerically, so start with the lowest number code.
Guys, sorry for responding in your thread, I hate offtopic, but I can't yet send PMs, and I hate to leave other people's messages unanswered!
As to the topic, I just wanted to reiterate that rather then poking the sky by replacing one element after another, I would first make sure I have proper diagnostics done to identify what it is exactly that's causing the issue. Yes, it's not free, but so aren't those sensors/cats!