[ImperialCrown]

If the downstream O2 sensor voltage pegs high or low, it will eventually set a fault code. I would replace it with an OEM NTK/NGK replacement and then see how it looks.
Over time the downstream O2 will shift the fuel trim, but if you keep disconnecting the battery to reset the PCM, it will never accumulate adaptive memory.
A cat fault code takes a long time to set.

 

[ImperialCrown]

Since it difficult to see the cam timing marks down in there, I use a small mirror and a straight-edge across the marks and cam bolt centers to make sure that everything is in line.
It is easy to be off a tooth and not know it as the cam sensor only watches one of the cams.