My 08 aveo sputters and runs rough when cold. I can't seem to figure out why, and only seems to be at idle. Once the engine gets up to temp it runs like a top. So far since I've gotten it I've replaced the air intake temp sensor, coil pack, plugs and wires as well as a new air filter. I've also sprayed out the throttle body with throttle body cleaner. Any ideas would be welcome!