Had a similar problem to this. Gradually got worse. No1 coil pack had a tracking line running the full length of the insulator. I did a temporary fix by warming the engine, taking out the pack and spraying with damp start, creating a silicone seal. Then wrapped in insulating tape and re-sprayed. I've been running fine like this for 5000 miles or so, never having had the time to replace the unit with the new one sitting in the trunk!