I installed a Roush rear valance with the square exhaust ports which did not come with the sensor ports. I disconnected the wiring but now get a check rear back up aid message. Is there anything else i need to do to disconnect the back up sensors?

 

Why not install them into the rear valance? You just don't like them at all?

 

I would take it to the dealership and see if they can completely disable the electronics that control the sensors.

I have the sensors as well and looked into swapping them into a new bumper but it's a bit more involved than I'd like.

Here's a guy on another forum that did it himself:
http://www.allfordmustangs.com/forum...-diffuser.html