ya know i had this same problem on my laser, sometimes out of the blue, there would be no vacuum in the lines with the engine running!...mike even saw this, the guage stayed at 0 and didnt move, went to boost fine, but i think it was just something to do with where it got tapped into...also i was loosing boost too on the 14B...17psi around 4800, then slowly dropped off to 13 or so by 6k