Another question would be, what is the max boost you can run with E85 on stock injectors and stay under the 80-90% duty cycle mark? 10psi?
Oh about 30 psi as long as you didn't go over 5000 rpm. J/k
Seriously alot more boost than you need to go very fast.
I regularly run around with my boost at 12-14 psi on 100% E85 and have all the performance I need for highway driving and some fun.
Octane wise E85 will support just about any boost level your turbo is capable of producing. If you include an upgraded (or crushed fuel pressure regulator to bump fuel pressure) you can probably run over 20 psi to about 4000 rpm, and 15-16 psi to redline. Due to E85's higher octane it will tolerate leaner mixtures than you can get away with on most gasolines.