Nowhere in this thread did I see one important item:
If your car is less than 8 years old and has less than 80,000 miles, the catalytic converters are covered under the Ford Emissions warranty.
I just got both of my precats replaced under warranty (no cost) at 78K miles by a local Ford dealer. Was getting a P0430 code, but the dealer replaced BOTH of the manifold/cat assemblies.
Steve