7.3 rough, missing when cold untill warmed up

[Hawaiankin]

Hello
2001 f550 Manuel 180000 7.3 stock eveything engine runs rough when cold Missing like on 6 or 7 cylinders can't barely drive for about 20 mins untill warmed up then fine all day until engine is cold normal temp outside 80degress I plug in engine warmer ( truck from new York) for 2 hours and starts fine no miss Any ideas

[sldghamr]

pull the valve covers and check the wiring that goes to the injectors.