More power, yes, but for a price. It takes more fuel to run E85 and it generates considerably more heat than standard gas.
To prove my point, the 73 Pay'N Pak ran avgas in it's Merlin from testing prior to the 73 season through the 77 season. Throughout that time, it carried between 60 and 70 gallons of fuel per heat. When it was sold to Madison after the 77 season, it was re-engined with a methanol fueled twin turbo Allison. The fuel tank had to be changed to 150 gallons just to be able to finish it's heats, which it still had when purchased by Ken Muscatel and brought back to Seattle two years ago.