Yeah its normal for a misfire every once and awhile. A Diagnostic Trouble Code (DTC) will only set if there is a consecutive misfire on a specific cylinder. I forget the number of misfires it takes to set a code, I think it's 5 consecutive. I could be wrong though, and im too lazy to look up the exact info right now.
Ford Motor Company's scan tool and software has a special feature called "Mode 6 data". In this data it counts misfires on each individual cylinder. There may be a few misfire counts on each cylinder without a DTC setting, which is normal.
Technically almost every ignition is a misfire, because you don't get perfect ignition and perfect combustion....
At any rate, a couple misfires here and there is no real cause for concern unless you get something consistent, and if that's the case, a DTC will set. (If the misfire profile is learned, MP_LRN = YES)
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2013 Performance White Boss 302
-Stock
2002 Mineral Gray GT
-VT engines Stage 2 N/A cams, full SLP exhaust, 4.10 gear...etc.