Great build, very cool.
I have no experience with E85 but is it possible that with 11.7-1, at 5000 ft and
7-10psi you might be getting into detonation ?
Anything is possible.. the cam I have has bunch of overlap, so I'm sure that helps.
Plugs look pretty clean. At least with detonation I would be seeing the repercussions in the porcelain. If anything I would be worried if I take it to sea level.