I have a 2008 CTS Premium with only 35.000 miles on it. I've had it for about 5-6 months now but recently I've noticed some "ticking" coming from the engine. It speeds up as I speed up and its usually a little more noticeable when I first start the car and drive, not as much as it warms up but still there. Also I've noticed some vibration when idling or at a stop light thats coming from the rear of the car. It comes and goes, sounds like the tail pipe but the dealer checked it when I got an oil change and said its secure. I've also started to notice that the rear windows don't always work on the first try and I hear a clicking in the door. Any help is appreciated.