The manifold appears to line up perfectly. Why I am confused is that it is in fact the same manifold and head. And, that I had all of the middle bolts - six of them - screwed in place. I don't think it's the gasket because I inserted an awl, very carefully, in the #6 bolt area to see how strong the obstruction was and it felt like the head, not a gasket. I do have a very small camera that I am going to peek down that bolt hole and see if I can determine more. I know you said that I could file the hole on the manifold, but would that be a cause for potential air leak?