e38 is the mix best for stock turbos and e63-e68 for rb turbos on n54 engine thats what my buddy ran when he had stock turbos now hes on rbs he has almost the same mods as you so it should be close to perfect if you have a n55 engine with FBO stock turbos e36 is perfect for pure stage 1 e58-e60 for pure stage 2 turbo e62-e64
im just telling you from my experience and from my groups experience Happy Boosting my friend hope this helps
btw here is a ethanol calculator
http://www.intercepteft.com/calc.html go there and scroll to the bottom
more details for California
in california we have 91 oct with 0 ethanol very few will have 91 with 10% ethanol but they will make it clear which is which the typical octane rating for e85 is 108 oct with 85% ethanol