How much more fuel does E85 need?

Somewhere between about 30% and 45% more by volume, depending on the assumption. LSX Magazine uses conservative BSFC values (0.80 for E85 vs 0.55 for gasoline), which is about 45% more fuel. Many tuners size with ~30% (gasoline requirement × 1.3). Speedway's injector chart runs about 19–25% larger injectors for E85 at the same hp. Size injectors and pumps on the conservative side and let the tune set the final mixture.