You probably already figured this out, but I have the same setup and was awkward behind the glove box. If you follow the wires from the SYNC module they go over toward the drivers side and down the right side of the center/stereo/dash kit area. You can undo the loom on the wire bundle and get at the SYNC wire from there. In my case it was a blue wire with an orange stripe. This was MUCH easier than hanging upside down trying to get at them at the SYNC module itself.
Hope this helps anyone trying to do this in the future.
2010 Black GT. Appearance mods only so far. SS center fog grille, DG Customs side and window scoops, SLP Loudmouth axle backs, Roush center console button, Roush white shift knob and boot, Metra touch screen dash kit w/ Kenwood/iDatalink NAV setup to retain SYNC.
NOTE: OEM grille, mufflers, and 401A shift knob w/boot are for sale if interested. PM me an offer.