The harness got the 5 volt reference signal from the TPS sensor for the 3 bar map sensor. The signal voltage representing the pressure was dumped into the temperature sensor that the turbo link software would interpret from the temperature reading the ECM provided.
Therefore the center two three position sensors bypass the TPS sensor (ie one goes into the sensor and the other the plug that you pulled out of the sensor), the other plugs into the harness the temperature sensor before the MAF sensor, and you know about the plug into the 3 bar map sensor.