Internal heat managment may also be partly managed with ceramic coatings. Porsche started using this with the old air cooled 964 motors in the early '80s. They only lined the exhaust port with it.
Sounds like you've already done some research, but here is a link to an article that hits the highlights in case others are interested.
A Look at High-Tech Engine Coatings and What They are Worth - Hot Rod Magazine From the results of the naturally aspirated engine it appears there is no difference in power production. The change is so little to be of significance. They didn't state temperature differences though.
So I guess I don't know what I'm talking about. Does anyone have some details on how Honda (or others) build motors to get maximum efficiency that might be used here?