Assuming that you are asking these questions pertaining to the car below your name, it would be a good place to start by removing the glove box liner and checking each line on the vertical manifold at the lower left as looking at the glove box. These are the lines leading to the vacuum pods that route air. If one of them is leaking, you will need to remove the dash and replace it. It is about a 14 hour job, so it's best to replace ALL of the pods while it's apart.

Hope this helps. If it turns out that there are no leaking lines, post your results here and we can go from there.