That funny looking boot is actually your coil for that plug. You have a coil on plug ignition system (wish I had that!). Try replacing your plugs first, then move to the coils packs. It is not uncomon to have a bad coil pack, however it is not the first thing to replace.
2001 F150, Black, Shortbed, Regular Cab, 4.2L V6, Auto, 3.55 gears, 4x4
Modified intake and throttle body, 265/75R16 Toyo All Terrains, Spicer greasable U joints & Moog ball joints, Delta toolbox, trans cooler and guage, Magnaflow muffler, Reese Class III hitch.