Did you just start running the E85 with little other modification, or had you put PTFE lined hoses, viton seals, etc in?
I wouldn't expect you'd have any problems going back to "neat" petrol. - I was just observing that a car that was built and mapped to race bioethanol had had problems with it destroying parts of the intake system.
On a similar note; I saw something else that said you should register for tax credits if you're going to use alternative oils as fuels (for example used chip oil).
If it's a fuel then you're supposed to be paying excise on it, and you can be done for tax evasion; apparntly that's no different to using red diesel in the eyes of the law.