I got back some numbers with a 91/E85 Flex Fuel tune from Delicious Tuning.
Extra Mods= DW700cc, DW65c Fuel Pump, Invidia catless front pipe and N1
Stock headers and overpipe
91oct Tune= 242whp (~280whp on another Dynojet that he tunes on)
E85 tune= 284whp (~320whp on the Dynojet)
So I'm thinking headers, overpipe and smaller pulley can probably get close to 400whp on E85