I have a 2005 f550 with a 6.0. The injectors were giving us fits so we replaced all of them along with new standpipe and plugs. It ha been running perfectly for 2-3 months and now, all of the sudden, this morning it wouldnt idle worth a crap. When you try to start it it would just start super slow and then finally catch and spudder and shake like only half the cylinders were firing.
We put it on our genysis scanner and got these codes:
P0611 ficm
P0262
P0270
P0277
P0278
P0280
P0284
P0528

We read that injector codes coupled with the ficm code told us the ficm was bad. We ha suspected this for a whole but this convinced us. So we replaced the ficm half she'll and it did not fix the problem. We have good logic and and vehicle power. Also ficm power never drops below 47. We are at a loss.

Also, upon first start up the blew black smoke pretty heavily.

 

Have you rechecked codes?

 

Its a long shot but try unplugging your fan clutch just cause P0528 is no signal circuit from the fan.If nothing changes i would check your battery voltage.