You made a good and important point. I forgot to mention that in my post so glad that you did. As a matter of fact I asked (e-mailed) Royal Purple and asked them if I need to add the friction modifier and there answer was no, that it was already in their 75W-140.
I then decided to ask here on this site and actually posted my question to Mike in the Superchips forum. He said what "he" does is ALWAYS adds the friction modifier regardless if its already in the brand you may be using be it Amsoil, Mobile 1, Royal Purple, Redline etc. So after getting that reply from Mike who does alot of high performance testing on the F150 I decided that I would add the friction modifier to the Royal Purple when I do get it. It cost like $5.50 from my Ford dealer for 4oz. which is what I need for my rear-end.