Vacuum Eco Guage

[aud180s]

Hi hope someone can help me with this.
My vacuum eco gauge has recently started to stick at the three quarter mark on gauge, it will 75% of the time drop to it normal position but at times will stick and remain at three quarter mark. Eco gauge does move up and down with revs as normal, also if it sticks and does not drop of its own accord if ignition is turned off and car restarted eco gauge always returns to normal tick over position. Engine revs are also increased when eco Gauge is stuck car runs at 1100 rpm. Any thoughts.
Cheers Dave