i have a 04 silverado with a 5.3. as i have noticed with mine and other trucks i have worked on and delt with, it has a studder at idle. almost like a very small misfire. doesnt effect anything or cause issues but i notice it mainly when sitting in it with it running not in gear. dont know if it caused by the ethonal in the gas or what but didnt know if any have noticed this or know where it comes from. it does not show on misfire data on scanner or anything. anyone with input?