Vac lines are vac lines. As long as they are where they get vacuum, they will work properly. (i.e. don't hook a vacuum line to a port on the blower outlet side)
Your gauge may not be accurate, or did you see a lower number before? Oh and I've cracked that plastic line that goes for the boost gauge before, right at the rubber coupler that holds it to the plenum. Make sure yours isn't cracked and leaking a little there.