am i getting false vacuum reading?

[94talonawd]

ok. here is the problem.
my car has bad vacuum at idle. note that my car does have an idle surge. the idle surge isnt bad, i dont even think it is idle surge. i just hear misfiring and my rpm moves around 700-900 rpm at idle. i tapped the boost gauge line to the fuel pressure line. when im at idle my vacuum reads like at 3-4. when im at idle reving the car to like 1,500 rpm, my vacuum will go to 15. i tried tapping the boost gauge to the p port on my tb, and it was even worse. i was getting 0 vacuum at idle. when i drive the car around the vacuum is pretty good. its only bad at idle. what are my vacuum readings supposto be? could i be having a vacuum leak somewhere? i did a boost leak test and i was only hearing a very little leak coming somewhere from the intake manifold or tb. if i have a vacuum leak will it cause my car to idle poorly?