Not to hijack your thread but I have a "chirp" sound (high pitch) when I decelerate from higher RPM's. It's a split second high pitch sound. I thought perhaps it was a loose belt, but it's tight...very little wiggle to it. Can't really pin point where it's from either --- but it's not affecting any performace.
I've been reading these threads trying to see if anyone has a similiar issue and how they resolved it.