Catalytic Converter Deficiency Code?

2006 Ford Police Interceptor 113, XXX miles. The car started making a rattling sound from underneath the car, most of it was coming from the passenger side front door underneath the car. Sounds like it's the catalytic converter or exhaust piping somewhere. I have a check engine light, it's a catalytic converter deficiency code. The code is broad, it doesn't give an exact cause, just that there's a deficiency. Soemtimes my car feels like there's some loss in engine power when I give it some gas. I'm not sure what can be the problem. Any insight?

I presume the code is P0420 or P0430 - "Catalyst system efficiency below threshold [bank 1/2]." Those codes are produced by the ECU when the downstream O2 sensor reports a high and fluctuating level of free oxygen in the exhaust leaving the exhaust. I have dealt with catalyst codes about a dozen times and none of the cars needed a new catalytic converter.

Anything that upsets the mixture or leaks air into the exhaust ahead of the downstream sensor can produce the codes. It doesn't have to leak all the time; once or twice a day can do it.

I recommend you have the loss of power checked first by somebody who knows Fords. That will probably take care of the codes. If not, the exhaust should be inspected for leaks.