Originally Posted by Jayhovah

The only NRTM you need for the Z1 Diff upgrade kit is to spring for the whiteline bushings over the ES Bushings. Paired with the Z1 Diff cover, the ES bushings don't really fit. According to Z1, you can just force the bushings farther into the mounting hole, but you will greatly deform a collar on the bushings and to me, this ventures squarely into incorrect installation of the bushing. Compared the ES bushings, the Whiteline's go in SUPER EASY.