Just to update on this issue...

Thanks everyone for your help and ideas. The problem ended up being cracks in the original #14 head.. at first I thought about replacing it with a used one, but decided to just go with a new #22 and eliminate it as a concern going forward. The car is in such good condition otherwise that it would have been wasteful to junk it, and I figure it should now last roughly till my kids are in college, lol. The repair will be right around $4k.

Anyway thanks again. Hopefully some of your suggestions end up being the fix for someone else having similar symptoms.