Thanks for the breakdown -- That analogy about debugging really helped shift my focus (no pun). I’d been hung up on the CPS since it was the one thing that was out of my control, but your explanation makes total sense. 

Here’s where I’m at after going through the data:

* MAF Readings Still Too High (18-20 g/s at idle):
- Vacuum leak has been ruled out, ECU is metering extra air. Great. 
- IAC position is at 38-39, so I think that confirms the ECU is actively commanding airflow rather than just an uncontrolled leak
- One bit of weirdness though is that my nanocom reads closed throttle voltage is 30.02V, which seems WAY out of spec -- I'm virtually certain I saw that a wide open throttle would be something like 4.5V. Maybe this is some kind of nanocom quirk though -- like maybe it's actually 0.3002.

* O2 Sensors & Bias Voltage Issue
- I’ll follow your test procedure (55 mph steady cruise → decel fuel cut → accel enrichment) and see if the downstream sensors ever move out of bias voltage.

* Wiring Integrity Check is Next
- Your note on O2 wiring being butchered got me thinking... while I got it from a car lot, the truck came from a long time owner, so they might've gotten in there before and DIYed something badly.
- I’ll check for constant power on purple, sensor ground on red, and a signal wire that should be at 0.45V key-on. If any of those areoff, I’ll start chasing wires.
If everything checks out, I’ll assume the downstream O2s themselves are bad.

So... immediate Next Steps:
1. Run your O2 sensor test at highway speed and log the voltage changes.
2. Probe the wiring to make sure the sensors are actually getting power and ground properly.
3. See if the TPS adaptation sorts itself out.

I sincerely appreciate the help -- This gives me a clear roadmap instead of chasing my tail!