Well, reading the "Tuning Notes" on the .pdf of the PC III install instructions, the grey wire is attached to the throttle blade sensor rather than the "TPS" like most other bikes because the R6 uses the "Fly by Wire" system rather than true cables to the throttle bodies. The GPX might actually be connected to the right thing, but see the instructions about not attempting to change anything without the bike being on the dyno above 9k rpms...