So I'm almost 7000 miles ... and I've noticed my chirps dissapeared around 6k ..
I use Mobil/Chevron Only now.
Shell didn't cut it for me.
Engine runs beautifully and it got a lot quieter :o
I run the engine pretty spirited btw so I heard it a lot when I come off freeways or stop lights ... I'm pretty pleasantly surprised
Maybe this is why the engineers didn't notice chirping - they drove it harder than most? :x