Have you replaced your fuel filter? Temperature sensitive , it is very important maint. 6.2 fuel filters cause many symptons. A good practice for dual alternators is to first disconnect batts and pull both alts and take to rebuilder ; freshen brushes, bearings and have them bench tested for output. over tightening alts will not cause driveability problems ; but can be rough on bearings. a bad or shorted cell in batt can also cause alt light to come on , as well as a bad rectifier. remember it is cheaper to rebuild than to replace. good luck