i have been getting 26.7 mpg running 87 only for the last few months. I don't think that's bad at all for mileage.
i haven't notice the exhaust changing the mileage at all either though. maybe all the gains are lost by me romping on it like any new toy.

 

93 All the time. Never have put anything less in my tank. Ever.

 

Ethanol is proven to be much more corrosive to your engine than gasoline. That's why it has to be a hybrid fuel.

 

for e85, i did say he did a "conversion" for it, i dont know what all it entailed

and i dont think that running 93/91 will make your car any more or less faster but its what audi calls for and is generally a higher quality fuel...

like i said before.. 4 tanks a month costs me $12 to give my beloved audi what she is supposed to have... its not a big deal $ wise.... just do it or get a focus or kia