[The Radium King]

it's not a head-off job to remove it, but probably a cam cover off job (and all the reqd cam holding tools) unless you got skilz and can dr. longskinnyfinger it out through the little hole in the cam cover. hack way to do a thread repair. first step would be to confirm your thesis - get your borescope in there and try to see the hex head of the anti-fouler. then check to see how the coil pack sits - did you notice it sitting proud when you removed it? then think to yourself - whoever used an anti-fouler for thread repair also had my cam cover off - do i trust any other work he's done? personally,i'd pull the cam cover just to confirm, remove the fouler and repair the thread properly.

edit - i presume it would come out just like a spark plug, so not even a need to remove/inspect cam cover. not sure how hard it would be to put in a helicoil with all that in the way, however (just trying to manage all the shavings) ...