Ok...more photos with color description. I forgot to add the the car was wired to run nitrous, but the PO removed the bottle (and I assume plate and solenoid since the intake is not plumbed) when he rebuilt the motor.
The first photo shows the 3 wires coming off the TPS (black, red green).
The second photo shows those 3 wires going into a connector.
The third photo shows where the white wire from the mystery connector was grafted into the either the red/green wire from the TPS.
The red wire to the mystery connector in the fourth photo (stay with me here) is spliced to a black wire that is bolted to the throttle cable plate which you can see in the second photo.
There is a lot of wire splicing and grafting on the car in general. The PO replaced the speedometer/tach section with all gauges, and he had to find an "old timer" to splice them all in and get them to work. I also see that the fuel injectors were spliced in...perhaps the 30lbs injectors had the wrong connecters...