i actually have sync in mine and used the harness to retain it. however i have done installs in other 08-11 foci without sync using the basic harness and running an acc wire with no issues. the display just shows "ford focus" whenever the car is on. doesn't cause any issues.
2013 F150 4x4 SCrew XLT 5.0L
Midwest Crew #22
Official FocusFest Event Planner