About 18 months ago, I tried 100 octane racing fuel along with a tune from Lito on my 05 with an E-Force supercharger. The car may have performed better, but it really wasn't noticeable. Then, I converted over to E85 right before the restrictions on covid hit. So I haven't had a true test of gains on the dyno or track, the ol` butt dyno has perceived a definite increase. I have a station less than a mile away that sells E85, so getting it is not a problem. And even with the 25% reduction in milage, the pump price is generally 30% less. So I come out slightly ahead.
BTW, after doing EXTENSIVE research, 90% of the horror stories you hear about ethanol are simply not true. They are exagerations, urban myths, and misinformation.
Two examples, 1. Every car site and forum and mechanic will tell you that ethanol will absorb water from the air. While this is true for pure ethanol, once blended with gasoline (E10) it does not. E85 may, because of the higher content, but it would be minimal.
2. Ethanol destroys rubber. True, BUT, rubber has not been used for decades in the fuel systems of vehicles for decades, it's all synthetic. So it is a moot point. If you have a carbureted car, do not use E10. It wasn't designed for it. But even then, the hydrocarbon blend ( Toluene, Benzene, Xylene, and ethyl-benzene ) they use in ethanol-free gasoline is much harsher than the effects of ethanol. Eventually the synthetic rubber will break down. The chemist I spoke to specializes in corrosion prevention of commercial/industrial water systems.