I had this EXCACT same thing happen to me back in January. Check engine light came on, took it to Autozone and got code P0420 - Bank 1 catalyst running below efficiency. Bank 1 is between the engine and the firewall and tends to fail first because of all the heat.
Take it to the dealership and have them fix it. Ford is obligated to replace the cats if they fail before 80,000 by the federal emissions warranty. You shouldn't have to pay a dime.
Oh - HTH isn't my name, that stands for "Hope This Helps"
- Austin
