· Former '05er
The engine runs open loop during cold cycle until there is enough heat in the exhaust to light up the catalytic converter and get the O2 sensor up to temperature. It usually doesn't take a long time, but during this time there is no feedback on the a/f mixture, the ECM is just using a value from the fuel map with a correction learned from the last time the engine was operating. This can cause a lope in the idle while the engine is warming up. It could also be a slightly dirty injector, but as new as your car is, it's not likely to be dirty unless you put some bad fuel in it.