Update: I installed the OEM header back on with new gaskets everywhere as well as a new battery. Fuel trims are better than than they were before but still very high. I also got the same 3 CELs as before after about 2 hours of driving since finishing everything up.
Here's another low resolution datalog:
https://datazap.me/u/rb28dett/nov-25-drive
As before, above 4500RPM everything is looking great. Its only below that the fuel trims are way off.
I have no idea what to try anymore...