[Steve Tinker]

John, before you go throwing money at the problem;
1) Try swapping the #6 coil pack (I know, again) with another cylinders coilpack just see if the fault follows the change over.
2) If the fault is still on #6 after above, while the wheel is still off run the engine after spraying water (from a hose) over the suspect coil pack and see if the engine stumbles more or if you can see and hear the spark tracking to ground.
3) Changing plug tubes and O rings won't help the missfire unless they are leaking - oil is a reasonably good insulator unless wet.....
4) If above tests are negative, then you are going to have to dig deeper as thstone recommends above....