Today I noticed while driving with the windows closed and the radio off, that it sounds like as if a window is still open. It's not the whistling sound the Bullitt makes at high speeds, this one actually sounds as if the window is open. You know the sound the car makes when you're on the freeway going 50+ MPH with the windows down, the "WHOOSH?" I get that same sound, but VERY faint (by that I mean I can definitely distinguish it, but it'll be for a second or two, go away, and come back.) What is it? It sounds as if it's coming from behind me to my right, but I might be wrong. As I said, it's not the whistle, because I already have that sound .