OK scratch the finding my lower rad hose for my pug thing! Those coils must have a ton of high voltage in them, or maybe high voltage and for a coil a decent amount of amperage. Try small rubber o-rings under your fiberglass trick, see if that stops it from arcing.
Using mylar sheet (a very heavy grade of Boeing drawing sheet) under the coil packs and down the plug holes was the first thing I did when I bought the LS several years ago. Has worked fine since, still no light show.