P0054 code help

[Henney]

I'm getting a P0054 and P0060 rear O2 sensor code in my 2005 LQ4 swap. I'm using a PSI harness and bought new AC Delco O2 sensors because the originals didn't match the harness plug. I did get the part number PSI recommended for the sensors. For exhaust, if it matters, I'm running Sanderson headers, H pipe and no cats.

I reset the code yesterday and started the engine a few times then drove and didn't get a code. This morning the code was present on my drive to work. Reading around here and ls1tech I checked grounds and fuses and everything checked out. There also isn't a short in the wiring from rub and the connections are solid. I looked at the freeze data from yesterday and today. Most of the numbers don't mean anything to me but I did notice in both cases the fluid temp was at ambient temp and the speed was 0, which to me says it's happening at first startup when the engine is cold.

So what's my next step? What actually happens within the ECM without the O2 sensor input? If the sensors work intermittently does the ECM use the data when it's available?