Yeah, I took a peek inside the air box (it is stock) and didn't see any debris at all.
Have been searching all over for this, and all I seem to find are people with bad couplers (which sound like a bunch of rocks tumbling in the supercharger) whereas this is only under boost. Speed makes no difference, and the second I let off even the smallest amount to get it out of boost (still can be on the throttle pretty good) and it stops. So odd.
Of course, since the supercharger only kicks in when actually in gear, I can't have someone sit in the car and "hit the gas" and listen under the hood as the supercharger doesn't kick in when it is in park obviously... Makes it hard to troubleshoot when I don't even have a location under the hood to look at....