I got a new 2014 silverado work truck whit 15 miles on it at first it was excellent, at about 200 miles the truck started to have a bad idle not smooth anymore and when its cold it can be felt more changed fuel types higher octane of 91 and tried E85 and no change. i already tuck it to the dealer 2 times at 2 different ones and they say the same thing,they say "it has no codes is working ok, it could be how the truck works after brake in and we have no updates or recalls for rough idle, we don't feel anything" they would feel it if it their truck and its a warranty issue. I been searching and looks like I'm not the only one whit that problem whit a GM truck
