My car is only running on 4 cylinders on a V8 4.6

Seems -- or is it? I would find it hard to imagine that you could sustain running at all if 4 cylinders were "dead". Base compression test is needed. Cylinder balance test. Relative compression test. Check for spark at all cylinders. Did the problem just occur -- after use of new wires? Are wires routed properly and attached to proper cylinders? Are they Motorcraft (Ford) wires?

Ignition spark - - Proper fuel delivery - - Compression - - - Which one is not present?