If your Taurus is not a flex fuel (e-85), it can damage your engine, since higher mixtures burn different than just a 10% blend. My guess would be that you could burn the exhaust valves, or warp the heads.
Your engine will most likely run lean causing the exhaust temps to go up. If your EECV can add enough fuel so the car won't run lean, your gas milage will suffer. Ethanol does not have as much energy as gasoline so more fuel is need for combustion. Sounds like a lose-lose proposition to me.