Firstly, how did you buddy remove the DPF out of the Ford? Did he just remove (cut it out and replace with straight pipe) and call it a day or did he do something to trick the computer?
AFAIK, there's a pressure sensor somewhere on the DPF. Maybe there's a before and after sensor. Whether these sensors are smart sensors (communicates back to the ECU) or dummy sensors (like airbags) is what I'm interested in.
What have you found when trying to disconnect it?