I have used a technique for years to determine where I have high voltage leakage. I work at night. You need that old weak flashlight.. weaker is better. You run the engine with the hood open and just wait for your eyes to adapt to the dark. Keep waiting. When your eyes are getting adjusted, you'll THINK you see a blue glow... usually not directly in the center of your sight, but just off to the side. You're almost there at this stage. Carefully angle around the car peering in the high voltage areas and you will start seeing the subtle leaks as erie blue glowing areas. If you're in need of a replacement wire, boot, or coil pack, it will be pretty obvious. I once found a faulty sparkplug this way, as it was glowing inside the porcelin. My problem at the time was a pesky lack of power problem that defied ID. The weak flashlight is all that's needed to confirm the position of the leak, but squint your eyes when using it so you don't take too long to re-adjust. It is very satisfying, and pretty spectacular to SEE the engine running this way. Of course you must be careful of the moving parts. Don't actually get in there without knowing where the spinny parts are. The Contour latout is pretty nice this way. You'll love the light show.
