Clean spot on the rear of both heads. External coolant leak? See pics

[BOP Nutt]

I was pulling my transmission and noticed a clean spot (ie no oil, grease, paint, etc.) on the rear of both my cylinder heads. Please see attached pics. Do I just need to go ahead and pull the heads and replace the gaskets? It is almost as if the head lifted and the coolant 'steam cleaned these spots'. BTW I did have a recent higher than normal boost incident when my hose slipped off my factory boost controller.

 

[lrayzer]

Pressurize the system and watch for pressure drop, (at first I though you were making a joke about a clean spot on a leaky Buick engine. !. like shall I add some grease here ??)
Analyze first before diving into that much labor, I guess it is possible that you have nailed it.

 

[jasjamz]

I'm not a Buick Pro but there is a water jacket there, if it had blown the fire ring you would be having more symptoms. That does not appear to be a copper gasket so I doubt it.