My 2007 CTS has 65,000 miles and over the past week some issues have come to life. The car has started to have a hesitation/bogg down when accelerating. A rattling sound also is made when the hesitation in accelerating. It also has started to idle rough. These issue only come up when driving around town at speeds under 40 mph. When driving on the interstate it has no issue. I have not had a check engine light come on. Any suggestions on what could be going on?