throttle body vacuum lines

I have done a bit of research and looked in the manual but i still can?t find what is meant to go the vacuum lines to the throttle bodies, as in what do they do. Do they go to a solenoid or just straight to plenum pressure?

I have seen some Z's with the ports just blanked off!

 

There are vacuum hose diagrams in the Nissan FSM, under the Section EF & EC.
Look in the Engine & Emission Control Overall System (EF & EC-4).

 

didnt see that one... EF & EC - 9 is a good diagram

 

I found this handy too... colour coded...

http://z32.wikispaces.com/Vacuum+Diagrams