At about 25 mph when I'm decelerating (coasting), my Model X 100D emits two short Darth Vader breaths. I wish I could be more specific than that in describing the sound, but if you heard it, I think you'd agree that it's a fairly apt description -- my 11 year old Star Wars aficionado concurs (as he imitates the sound). Anyway, I'm just curious. What is it? Has anyone else heard this noise? May the force be with you.