Once again, know why and what you are cutting from your CDI. Look at “YOUR” 07 WR450FW service manual. The “Gray” wire is one of two grounds for the CDI unit and is not a mod. There is a link somewhere in this web site where a guy cut the wire and could not get it started afterwards. Here is a link to help educate you.
The article you refer to address's the 03-04 models. However, the 07 wiring diagram show's the wires as you suggest. But, I did disconnect the gray wire from the CDI connector just as the AIS removal kit suggests. The bike not only runs, but runs very strong. There are many posts in here about disconnecting the "Gray" wire and the results from having done so. Some suggest that the difference was so much, that they reconnected it until they got used to the bike. Mine is staying disconnected and stowed.