I was idling in the driveway today and gave the throttle a "blip".  Hmmm.  Did it again, but this time with a little more force and the door driver's door open, ear toward the side grill.  I discovered that before the rpms climb, there's an immediate "flat spot", for lack of a better way of describing it.  I also heard what seemed to be a flap opening/closing, causing a thud before the throttle responded.
Anyone else experienced this? 2002 S btw.