Difference between the Diablo Tune and the 91 Octane Tune

[supachim]

I have a Predator U7191 and was wondering what exactly was the difference between the normal Diablo Tune, which states on the website is for premium gas, and the 91 Octane Tune. Correct me if I'm wrong, but isn't 91 octane premium gas? So... I'm a little confused. Any help is appreciated. Thanks!

[mikel]

The 93 tune has more timing than the 91 tune.
The 91 tune is designed for those who do not have access to 93 octane.

Thanks