Another sign of reversion is steam out the exhaust on warm start-up and idle.

Cap'm Kurt, that flap at the end of the pipes move is simple genius. Cause I hadn't thought of it.
My engine is out for head work, not valves, I've been getting idle fouling on the ten minute ride in and out of the marina. I cannot reach the tips when the engine is in the boat. I'm going to run it on a stand before installation anyway, and I can check it then for reversion.
I have the EMI aluminum manifolds with extra height risers that add the water at the ends. I've been getting head gasket fails. Who'd expect reversion with a middling cam?
I love a good easy idea.