So got it running today! Turns out there was +5V coming out of the correct pin on the ECU but not at the TPS end.

Fortunately the +5V was working at the MAP sensor and they share the same 5V line so we cut the 5V wire at the TPS (just in case it was shorting to ground somewhere further back) and ran a temporary wire spliced in from the MAP's +5V.

And it runs! And it keeps running when you give it more throttle, all the way to full throttle.

The idle is very rough and there are a few other issues but I'll wire up the CEL straight to the CEL pin on the ECU and see if I can read some codes that way.

Very excited