nothing more than your original engine
perhaps , a tune if you don't trust lambda probe before and after catalyst (which alreday done a great job in OEM prog.) Long story E85 and engines...Depend also of the real part of ethanol by galon...In EU., in winter, we have more than 35% of regular gas in the E85, (they should call it E65) no risk to fill the tank 50/50 and more...