ISO is for Isolated boost control, now controlling directly and no longer adding over stock boost. Nothing magical or voodoo about it, you should use it its a great enhancement.
For the record, the Procede use this since day 1 and its one of the reason I prefer my Procede tune over my JB4. I haven't tried the ISO JB4 yet, a bit lazy on switching tunes again. But I will when I'll test the Cobb AP next week I guess...