I have on 03 F350 that recently started running rough as if dead miss at idle and is blowing grey smoke. No ses lamp. Where to start? Im assuming a bad injecter due to the fact it acts as if missing on 1 cylinder at idle. Its blowing fuel smelling grey smoke. I did change the fuel filter for the heck of it but made no change. I can tackle most of the work but need ideas on diagnosing.