ET, I haven't heard the noise that you are talking about (I too have an XE 2WD), but it sounds like you might be hitting the stops when turning, and then when you ease off the wheel to straighten out, something in the steering gear is "easing" back into place. Might be a tie rod end or ball joint popping when this happens. My '03 S-10 did the same thing when the wheel was turned hard one direction or the other. I don't think it's anything to worry about, but you might want to jack up the front end and have someone turn the steering wheel to the stops in both directions while you watch the steering linkage and suspension components.