My sr20det makes this weird sound that is accompanied by a change in the ignition timing when ever decelerating.
The video is at idle, but it does it with load as well. Say I'm cruising in 5th and let off the throttle to slow down. It makes the sound nonstop, until i give it throttle. Timing drops to zero as well.
http://youtu.be/kSKNXEhVXDo