It's the ethanol in the 94 being the reason for your loss in fuel economy.
for a Turbo/Super Charged application (shoudn't really be including S/C lmao) ethanol can be helpful since ethanol burns "cooler" resulting in lower combustion temps making it safer for m0ar boost, aggressive timing or leaner AF ratios...hence guys making retarded amounts of power running e85. Will the 10% in the 94 help? It should. How much? who knows!