Vacuum leak?

Don't get ahead of me here, but, on my daughter's '03 Neon SE, only when the A/C is on recirc, there is a squeaking noise coming from under the dash. The noise is not that noticeable and is probably the blend door scrapping/scratching against the ducting. The noise occurs about the time the transmission shifts, hence, during a vacuum change (my assumption). I'm not so concerned about the noise so much as I am wondering if there's a vacuum leak elsewhere that is affecting the vacuum on the blend door. In other words, could the noise under the dash be an indication of a vacuum leak elsewhere?