Need help with CEL P0153, P0159 and P1448

OK so about 300 miles ago I had the following codes (I put question marks so I can be corrected in case what I wrote is wrong):

Pending Trouble Codes:
P1448 (Bypass thermocouple?)
P1449 (Left cat thermocouple?)
P0159 (Bank 2 sensor 2, which if I understood correctly, is the downstream O2 sensor on the left side?)

Trouble Codes:
P0153 (Bank 2 sensor 1, upstream O2 sensor on the left side?)
P0159

It's also worth mentioning that when I dropped the car off at the mechanic for an oil change, the SDL came on briefly when cold. This is the 2nd time it happens in about 3 months although when it happened last the car was hot.

I then swapped the cat ECUs from left to right and also swapped the thermocouples between the bypass and the right cat. Proceeded to clear codes and after 250-300 miles I have these codes:

Trouble Codes:
P0153
P0159

Pending Codes:
P1448 (I cleared the codes again shortly after and this one has not come up again)

I obviously swapped the cat ECUs and thermocouples around to see if the problem would follow them but it's not. What is also baffling is that I have new downstream O2 sensors with mini cat extenders. I also have hyper flow cats.

So what do I do next?

 

Interesting, don't think I've seen that mentioned yet. Is the Moronic that off that one O2 sensor would work with the extender and one wouldn't?

 

I never had stock cats on it, bought the car with straight pipes but those were swapped out right away.