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?

 

Slow response codes are often attributed to rear O2 sensor readings. If they are known good, then consider removing the extenders.

 

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?

 

Does it give these codes with stock cats?

 

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