I have tried a few things with some success so far.

First, I replaced both my O2 sensors and the throttle position sensor. This has seemed to fix my power loss issue, but before long the CEL came back on with P0171.

Second, I replaced my IAC valve. This initially seemed to fix the RPM surging at startup and remove the CEL, but it both have come back now. It does seem like the surging is less severe and common.

I think the next culprit is fuel pressure, but I'm interested in thoughts on how to approach this issue.

Photos below:
1. Downstream O2 sensor
2. Upstream O2 sensor
3. Comparison of old and new TPS
4. Old IAC valve

Attached Images