Your cat-converter is probably bad, especially if it's an aftermarket part. You should have ZERO CO left over if the converter is working properly. The state of CA mandated a change in converter quality starting this January. They have to guarantee them for 5 years and they have to have a CARB EO (Exemption Order)to be legally sold now. I've seen the old style aftermarket replacement Cats fail in one year, and barely pass NOX readings when they are new. They skimped on the Rhodium in the substrate for cost reasons.

As far as the EGR is concerned, find the factory test procedure and see if the EGR valve is actually working. Usually if there is a circuit problem with the controls, it would throw a code and turn on the light. Most CA Mitsubishi's had a EGR temp sensor that if it doesn't see the temperature rise when the ECU turns on the EGR valve, a code will set and the Check Engine light will come on. EGR should come on at partial throttle, medium to light load, engine fully warmed up.