Did you adjust your timing at all while running the straight E85?
I never claimed I run E85 in my CRX. In fact, I don't run E85 in any of the family's vehicles, as I don't have any cars that are designed for it (and would therefore be concerned about ethanol's corrosive effects, when used in too high a concentration). However, a co-worker of mine has a flex-fuel van, and reports that his van's FE only goes down about 10%-15% on E85 (much less than the BTU difference would indicate).
NOTE: He can currently get E85 for around $0.90/gal cheaper then E10 (although he does have to drive about 15 miles out of his way, to get that E85 price). But even with the extra trip to fill up on "corn juice", and the lower FE of doing so, he still thinks he is saving a fair amount (and given the much lower price of E85, I think he is right).
As to my CRX, I'm still trying to figure out which fuel my car like's the best. Most of the stuff around here is E10, and so that's often what I use. But there is one station advertising "no ethanol" in their fuel i.e. presumably pure dino juice). However, when I last filled up at that station, both my power and my FE went down some (even though the higher BTUs of pure dino juice, should have resulted in a little more power and FE)! And when I later filled up with E10 (on the next tank full), the car's power picked up almost instantly.
So I'm really left "scratching my head" as to what fuel to use. And while it is clear that total BTUs/gal makes a difference in FE, it clearly isn't the only factor in FE. And in some cases, a lower BTU fuel might actually give you better FE in some engines (especially if the engine in question, is happier with the burn properties of the slightly lower BTU fuel).
I was talking to the clencher about the timing, sorry for not being more explicit!
Anyway, that is odd. I've never noticed a difference with any gas, anything in the tank, any change in intake, exhaust, nothing. Hell, I can't even tell the difference with MPFI besides the sound, but mehbe that's just because I never hit 2k rpms even,