Persistent Engine Code P0304 with check engine light
 

We own a 2014 Convertible Mini Cooper S. About 2 weeks ago, we went out driving and about a half a mile from the house, it started running rough and I got a "Reduced Power" warning. I returned to the house and started looking up info on this and other forums. It was a cylinder 4 misfire code and all indications were a need for a coil replacement. As it was time for an oil change anyway, I ordered the ignition coils, the spark plugs and everything needed for regular maintenance. The plugs are Bosch and the coils are Delphi. I did all of the maintenance and replaced the coils and plugs and started up the car - it ran great and the "Reduced Power" warning went away. It operates well in both normal and Sport mode. The problem is that the check engine light is on, indicating a cylinder 4 misfire (P0304) and my OBD2 tester will not clear it and I've driven it over 100 miles since doing all of the maintenance (to try to clear the Check Engine Light). Is there something else that I am missing?