Sorry but every time I see this statement I have to correct it... nothing personal... just nit picky like that
E85 is actually only ~96 octane using the Canada/US scale... the fact that it burns so much cooler is why it seems higher...
And I dont know if you did this and didn mention it but its a good idea to replace your fuel filter a couple times (i did 3 to be safe) in the first 1k miles as the ethanol will clean out a bunch of crap in your fuel tank/system...
I am seeing similar mpg changes that you are having as im mainly city aswell...
Matt, been DDing my car for over a year on e85 no problem... in fact I just installed the rewire about a week ago... and Im running a 2.8 on a genV...
our stock pumps are boss....