From what I understood the fuel system and engine have to be modified to run e85. Running it in a non-e85 engine would result in seals being eatin up by the alcohol. I mean Im sure it would run no prob, but eventually you'll have some major issues.

 

The problem is that E85 does not have the same BTU output as gasoline and you have to retune the EFI to add much more injector pulse width to keep it from leaning out as well as recurving the timing. Not to mention the corrosive properties.
Kinda like running a race car on alcohol vs gasoline. You need special gaskets in the carb and you have to jet it much richer.
With proper fuel components and the right tuning, it can make a lot of power.
There is a Jack Roush drag car that has one of the 7L versions of the new 6.2L engine running on E85 that runs low 7's in the 1/4 mile. It takes 2 injectors per cylinder to do so.

 

i use e85 every once and a while...on my 07 4.7 flex fuel...and LOVE it...but HATE the mileage..i normally get 14 but with e85 i get 10 on a good day!! but u can feel a noticeable gain in power! and the engine note is a tad different..but yes it is not a good idea to run 85% ethenale on a gas motor that is supposed to have about 7% ethenale.

 

some dragsters use 100% ethenal and get huge gains in power!

 

drag cars that are custom thought out and built are way different that cars made on an assembly line for a regulay joe