Timing custom option (on 6.0)

[eabrust]

All my searching the forums about the custom option menu items seems to be responses related to the gassers...

Does the 'timing' custom option actually change the injection timing on diesels (6.0 in particular)? I've gone both + and - a degree, and can't really tell that it does anything noticeable, and I didn't want to go anymore in either direction until I confirmed it is doing something. If it is making a change to the actual timing, I assume + is advancing, correct?

thanks,
Eric