Valve for tank-Benzingas feed disconnected ??

Hello community!

For a few days now I am finally again among the active V8 drivers ! Not the most beautiful but runs great !

Now you look and fiddle at the new car here and there, and today you had to find out that the valve for the
Tank-Benzingas feed ? (seat under/next storage tank for cooling water) was literally stuck off. The situation is as follows:
Hose from the tank and E-plugs were on, but vacuum and feed hose to the engine were removed and motor-sides were closed with screws as plugs.

1. Why would anyone do that? Is there a deeper sense or was it just forgotten after a reperture?
2. If this valve is "clamped" like my one, can it generate a higher fuel consumption?
3. How do I know if the valve is working properly?

Now I have "clamped" it again and am approx. 30km, but no difference was found. Engine's running the same way.

For information on this matter, I would be very grateful!

Michael