Just to clarify, the Euro4 is a motor driven EGR, if you have the vac operated one it is not Euro 4, the electrics on the vac operated EGR is just a position sensor giving feedback to the PCM (Powertrain Control Module, Ford speak for ECU). The position sensor sends 5 volt reference 0.3 volts (closed) - 5 volts (open) back to PCM

As you say, the actual valve is operated by vacuum by a solenoid that is PCM controlled, the PCM will send a PWM voltage to the solenoid to operate the EGR.