slight hissing sound of air flowing thru vents

[slipkids]

does anyone know why i have a slight hissing sound of air, coming thru my vents. The ac is closed, is it possible i have a vacuum leak. I dont seem to be losing any power. I smell a slight potent odor in the winter time, as i have the windows up. I am baffled, as this occurred ever since my radio was stolen from me, and the person did a neat job in taking it out, but is it possible he damaged something from the interior side of the car, where the radio was housed??

Confused in New York
1993 thunderbird sc 3.8L
steve