Generally speaking, turbos should run on minimum 98, e85 runs cooler and get higher figures, however, to get your car tuned to e85, you need both the pump and injectors to suit e85, with my setup, 300kw on 98, would get like 350kw on e85, but that would be a good $1000 to convert to e85, 91 is pretty much the lowest octane rating a car can run at, e10 is 91 with I believe upto 10% ethanol, neither I would recommend running with turbo, but, that's me.