You will need to upgrade your injectors and your fuel pump. We recommend using our Admin 650 injectors or ID1050X injectors and the AEM 340 fuel pump. You will need to be nearly empty when switching between premium fuel and E85. If you have installed a flex fuel sensor you can refill at any time with either fuel. When coming to the dyno to tune for E85 please remember to show up with less than a quarter tank of premium fuel and bring 10 gallons of E85 with you in VP fuel jugs.