I don´t really see what you are trying to do here? A tuning formula? If what I think you think that is (?), you are way off! There is no such thing as a set formula for tuning. All cars are different (albeit, a R34 Nissan Skyline V-spec II and a R34 Nissan Skyline N1 are not that different...), but you can´t really say that "this setting will always work", simply because it won´t. Or saying "this type of car should always be equipped with a turbo, and not a supercharger" isn´t right either.
Making a .xls tuning formula would take a very long time, since you´d almost have to make one for each car!
Or maybe I just don´t know what you mean.