Hello, I am John, a Ford dealer technician.
I hope I can help solve your problem quickly and accruately.
123 is on the rear bank 456 is the front bank.
The lean codes may be a sign what is causing this. You could have a bad mass airflow sensor or a bad fuel pump. There could be other things but these are the most likely. To see if it is the fuel pump use your scan tool to read freeze frame data for the lean code. If it set the code at highway speed then you have a bad fuel pump. If it set the code at idle (0 mph) then you have a vacuum leak. This could also be what is causing your miss. Number 4 is farthest away from the fuel supply so if there is low fuel pressure this is the one that will miss.
I hope this answer has been helpful to you! If you have any further questions please feel free to ask.
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I listed this above.
Rear bank is 123
Front bank is 456
The coil and plug you need to check is on the front valve cover all the way to the left.
Sorry, most people are just asking where the cylinders are at. The actual firing order is