Prior to the start of the STAR smog check program smog technicians were simply instructed to visually ensure the catalytic converter was present and that appeared to belong to the vehicle; fit looked right and number of CATs present were correct... and so that is how your Mitsubishi has passed the smog inspection in the past.
Since the STAR smog program started, a smog technician can lose his/her STAR rating if they don't ensure 100% that the CAT on the vehicle is specifically built for the vehicle; the Executive Order numbers must be present and match the required numbers for a 2003 Mitsubishi Eclipse.
Your only recourse now is the replace the catalytic converter with an aftermarket model designed specifically for your Mitsubishi Eclipse. We recommend shopping around for the best price. Aftermarket CAT is available for your vehicle; which makes it much cheaper to replace than needing the original catalytic converter. $800 sounds about the right cost. If you do a bit more searching (and calling around) you might find a shop which can do it for a little less.
