I do not believe that a 5.4 will idle on three cylinders. In more specific terms, I do not believe that you could disconnect the 5 coils that made no difference, all at the same time, and still have the truck idle.
I do believe that disconnecting them one at a time made no apparent difference.
Conclusion is that 3 cylinders are strong, 5 are weak. Since you didn't bother to enumerate the strong and weak cylinders, I have one wild guess:
One bank, 4 cylinders, is messed up, either the cam is off or the fuel rail or some other component is malfunctioning. One cylinder on the other bank has a bad cop or injector.
If you do shoot the truck, please specify which cylinder and caliber.