The only reason I can think of that you'd *need* a new ecm is if you wanted to run different blends of E85 and unleaded. Then you'd need a flex fuel sensor and the ability to modify the fuel pulse for varying stoich ratios.
Other than that the stock ecu would work fine, with the proper calibration.
I come back to Lee's original question and I don't know why one would do this on a naturally aspirated engine. There is much less energy in a gallon of ethanol compared to pump gas so I can't fathom how it makes more power normally aspirated. Now if you're running boost and can benefit from the charge cooling effect then ok. But that's not the situation that was proposed.
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