[DickH]

You can go with whatever settings you want, as long as you pick the important ones correctly (gear ratio, rear o2 on or off) If you are putting 91 in, go with the 91 option. You shouldn't hurt anything by choosing something else. I have mine set with the timing set as far as it allows, its lean some, and I have it set for the highest fuel option (forgot what it was) and have not had problems. I cant honestly say I notice any difference between settings, or even with or without the sct tune.