[jimmytroanoke]

You say the wires are sound. Is that a visual or did you check them with an ohmmeter? visual "looks good" means nothing on plug wires. I've gotten bad ones out of the box. If all 3 of the misfiring cylinders are on the same coil pack, have that checked. If all else fails, open the hood on a dark night and take out the bulb. Start it up and look for arcing. I've found bad wires that way. Check firing order. If you used Bosch plugs yank them. The only plugs that last in the modular V8s are Motorcraft from the dealer. Did you put dielectric grease in the boots? Did you detail (spray off) the motor? The way the plugs are oriented any water is just going to lay in the holes and cause a misfire. If all that fails, look at injectors - they will also cause a misfire code.