Googled it, apparently a really common issue. I think you 100% correct, I need to drill a hole to let it vent. Its weird, because the cap has a vent.I've had the same issue with low miles and rust inside my MSD distributor. A member here years ago told me to drill 2 very small vent holes in the cap near the base to allow the moisture to vent out. I did this and it seems to work.