Turns out my 06 CTS 2.8L with 47k needs a new torque convertor. Took it in for a few things (parcel shelf rattle, door rattle) and had them check out why my RPM's were bouncing by 1-200 rpms on the freeway at a steady speed. Good thing its under warranty still by 3,000 miles, I would hate to find out how much this would cost. The car will be there through next week wednesday while they order the part and drop the tranny. Anyone else have this happen? I baby the car and its mostly HWY miles on it.