When I loaded my 91tune it first saves the stocker. How does it deal with going from 91 to 93. Same way? "Saving 91 tune --uploading 93".
I don't know how the SCT deals with files and how much it can hold. I don't want to loose or overwrite files.
No, The 91 octane is programmed into it as is the 93 octane - the very first time you use it it saves the stock tune in memory along with the VIN. Any changes you make to the same VIN vehicle is doesn't re-save. Flashing time is cut in half. If you return it to stock, between tunes, which is not necessary, then next time you put a custom tune into it, it will again re-save the stock tune.