Same thing is driving me crazy too. See the glitch stuff in giants forum. My ignition guy said not to shield the plug wire because after 20 or 30 flights the carbon core will get fractures and if a leak path (ie plug wire shield) is available it can cause more problems than it will solve.

If you turn off the lights and hold the plug wire by the insulation you can see a glow around it next to your fingers when it fires. spooky.