i just installed a greddy boost gauge 52 mm version 2.(amber light). recently i noticed that after i turn off my car and turn it back on the dial does the self test but then stays at 0. when i start driving it shows boost build up but when i let off the gas it goes back to zero does not show any vaccum. eventually it starts showing vacum pressure after a couple of minutes. if i start the car and let it idle for a couple of minutes it will eventually show vaccum pressure as well and work fine. the weird thing is that if i turn the car on and off sometimes it shows vacuum pressure imediately, i'm puzzled. can someone help.