I'm pretty sure your flex fuel sensor detects how much e85 content there is and then through the ECM makes all the adjustments for it. You can mix e85 and regular gas obviously. As far as our turbo buick motors, I have to change chips if I want to take a trip or something where I would want to use regular gas. I ordered 2 chips when I switched to e85. My buddy just made the switch in his Ttype and with no other changes went 3 tenths faster in the quarter over his previous Alki setup.
