How much boost/HP do u want?
Assuming max HP(490hp). Since stoich on e85 is 9.7 and gas is 14.7. u need about 50% more fuel to be at lambda 1. If you use the RC eng injector calculator it says you need 1000cc injectors to flow 490hp on gasoline. so you should need 1500cc injectors to flow 490hp on E85. U can push the IDC up alittle to 90% and you could get up to roughly 400chp on those 1000cc injectors. This is pump gas corrected for the E85 so you could get alittle more HP because you can bump the timing up because the e85 has a higher octane rating, but you need alot more flow for E85 to get the same HP roughly as pump gas because of the lower energy density.
max boost on those injectors with e85 would probably be around 30psi at 4000rpm and you would have to taper back to 18psi at 6000rpm. If you go over 18psi at 6000rpm your injectors might not flow enough. This would give you around 400chp(325whp??)@6000rpm.
I would upgrade the injectors just so you can actually reap the benefits of E85. You could get more HP on those injectors with pump gas.