My boost gauge used to sit on zero obviously when the car wasnt running, but now it sits about 4psi below it, is that it fooked or will i still get an acurate reading?

 

well i would assume it would be 4psi down!

 

No, thats normal, and it is in fact measured in Hg (mercury), and not psi, this shows your engine is drawing a vacuum at idle which it should....

0 represents normal atmospheric pressure, anything above this is positive pressure i.e. Boost anything less is vacuum....

hth