I have a stock 2008 CTS base that has a consistent acceleration vibration. You can feel it in the steering wheel and shifter. It occurs at all speeds. I just took it to the dealer and they said that all they could do was download an ECM update, but it would negatively affect fuel mileage and could make the problem worse. The tech that drove it said he's felt worse and he would just ignore it. It's hard to have a Cadillac and accept a known problem like this. Has anyone else had this and is there a true fix?