Personally, I'd do the E85 switch before the turbo. You may find you're happy with it and less problems of having things apart. You could do a FlexFuel kit and injectors/pump, and you could size the injectors to a size that would support whatever turbo you're looking at. If you never upgrade the turbo, you'll have a good FlexFuel setup. If you do swap turbos, you don't have to mess with fueling.