Maybe the higher humidity up there causes the issues, but down here E85 rules. I was just in a group conversation with one of the best LSx tuners in the country, NicD (who also tuned my SS), and he said E85 will make a little more power than C16.
2015 F150 4x4 3.5 Ecoboost
2002 Camaro SS, new turbo install in progress...
2005 Neon SRT-4, Big wheel stage 3, E85