I think what you might be hearing is the pinging coming from the engine at light throttle/low revs. It's discussed a few threads down from yours. I took my car in about a week ago to do software updates and it's less, but still there. I'm hoping a tune will clear it up completely.
I just picked up mine 2 weeks ago and noticed this right away. I thought maybe the dealer put 87 in it or something when I picked it up, but 2 tanks of 91 later, it still does it.
I'm hoping after the break in period and then a tune will resolve it.