What I did :
PT7 goes to IN at boost control transistor (top of board)
Boost control transistor Out wired to port 4O on the adapter board (which is port 2O of the original ECU connector).
This red wire originally goes the the MAF sensor, which you no longer have/use. This is wired to your new EBC. This is the grounding circuit - the ECU controls the EBC by opening and closing the ground leg of the circuit.
You then need to have constant +12V power wired to the other terminal of the EBC. You can use the white/red power feed that was previously used by the MAF. So, you are using two of the wires from the original MAF connector.

 

One small correction, although it does not really make a difference. For the +12V power supply, I used the +B white/red wire from the diagnostic port since it was closer (but this is the same circuit (1B) as the white/red power wire at the MAF.