your plugs are not black though, that would be a sign of rich. If you don't experiment with something (i.e. fuel pressure) you will not learn anything.
This and Coyotes comments led me to believe it cannot enrichen enough, and this is the last I'm gonna say about it cuz time=money
from:
EPA baseline MPG and the effect of E-10 - Tampa Gas Prices
"I had a car that ran good on regular gasoline but lost more than normal miles per gallon on E10. A small vacuum leak was the problem. Not enough of a leak to effect gasoline but just enough to keep the car from adjusting the fuel ratio to run good on E10. "
Think about it at least.