Recirculation flap vacuum servo

[Antsa]

After taking out my blower box I noticed that the recirculation flap is operated by a vacuum servo. The servo connections were like in the picture, one hose from solenoid to servo and one from solenoid to open air. My guess is that the open end hose needs to plugged to a vacuum line from the intake manifold? But why is the recirc flap operated by vacuum instead of electronic motor? Since in our intake manifolds have so little vacuum in them (couse of the turbocharged engine), does the recirculation not operate under boost? Please enlighten me

[newsh]

It's not connected direct to the IM. There's a vacuum reservoir behind the front wing.

[Antsa]

Are there any schematics about the vacuum plumbing? I guess there has to be a one way valve somewhere? And why is the recirc flap operated by vacuum and not electrically?