I remember [MENTION=3416]WRB_STi[/MENTION] was running a Haltech ECU with a flex fuel setup in his last Evo. Besides something like that setup, you'd need two separate tunes, one for E85 and one for 93. Some people don't have any problems with separate tunes, but others have issues with the E85 that's available to them. Often times, what is advertised as E85 isn't actually 85% ethanol. This is especially true in areas where seasonal temperatures swing widely, making the ethanol fuels considerably different in content between summer and winter blends. Obviously, this screws up your AFR and could be detrimental to the engine. I know one guy in particular that has 4 different "E85" tunes because the stations he gets it from swings from E70-E90 throughout the year. He carries around this ethanol content test kit with him everywhere, tests the fuel every time he fills up and chooses the appropriate tune for the fuel content. To me, that's just ridiculous, too much screwing around and too much room for error.
If I really wanted to run an ethanol based fuel, I'd probably get a Haltech ECU with flex fuel and then I wouldn't have to worry about the fuel content every time I fill up.
It probably goes without saying, but you'll also need considerably larger injectors and a more capable fuel pump to run ethanol fuels.