The vacuum diaphragm actuator (BBV) has two ports, one on the top and one on the side. The port on the side is going to the electrical solenoid that gets commanded by the computer. The top port goes to the top of the supercharger that has manifold vac.
Looking at the solenoid from left to right the left side is connected to the same VAC/BOOST line that goes to the FPR and the right side goes to the bottom port on the BBV.