Ok, so I can't seem to get around code P0303 and P0455. Over the past few weeks I have replaced the plugs, ignition coils, fuel injectors and purge valve with no luck. I now am assuming it's either an air intake issue or a short. The only time this will occur is when I am at a stop light and the engine starts to idle down...after about 5 seconds the misfire will occur. This does not happen when I am on the highway which is why I'm leaning toward an air issue. I have not replaced the MAP sensor but might do that next just for the heck of it. Am I missing something? Any one else have a similar misfiring condition that they can't seem to get rid of?