I have a 2003 f350 with the 6.0 liter Powerstroke and it is running rough at idle and is missing as revved up. I pluggged the scanner in and it pulls code # PO278,CYL 6 Contribution or balance fault. How do I repair the problem and just yesterday I plugged the scanner back in and it pulled the same code ,now its Cylinder #7. Thank you in advance!