Just my 2 penneth:
Due to the fuel situation here in the UK I contacted Ralliart yesterday regarding octane boosters, in case the only fuel I could get was 95RON.
I spoke with Toney Cox, who is their technical director, and he stated that at no time should I use ANY octane booster in my car, I would be better off using 95RON fuel (minimum amount) and driving VERY carefully, i.e. no more than 0.5-1.0bar boost, until I could find Super again. He stated that octane boosters are distinctly BAD for my car.
Now I don't know if this applies to standard Evos, as my car is an RS450, but I would think it would be wise for you to check, I'd certainly hate to think of people ruining their lovely Evo engines using this stuff http://www.ltregister.force9.co.uk/graphics/TooHappy.gif border|EQU| 0 align|EQU| middle >
Cheers,
Alan