On the odd occasion i've run it in my SSV-Redline (OTR, extractors, exhaust and tuned) i drop from 450kms/tank on 98 to 300kms on e85 for really SFA power gain, you feel it but nothing to write home about. In a turbo car, and tuned for it, you get good gains but NA it's nowhere near worth the extra expense!
There's also no such thing as magic spark plugs that will give you extra power!