Nissan Repair: emissions, fuel injector cleaner, nissan frontier

Question
My recently purchased 2001 Nissan Frontier 2.4 cyl. was running rough and the service engine soon light came on. I installed new spark plugs and wires which fixed the problem, but about 25 miles later the service engine soon light came on again and the 2 codes indicate 1. egr flow malfunction, and 2.catalist efficiency below threshold. It does not accelerate well and seems to struggle for power. Can you clean the egr valve or must it be replaced? Hope I don't have to replace the catalytic converter. Any advice would be appreciated.

Answer
It sounds like a fuel injector is stuck open.  When you get the efficiency below threshold that is usually the case.  If the egr is malfunctioning you need to check to see that the egr is working correctly.  I would remove it and see if the port is plugged.  On the fuel injector I would get a fuel injector cleaner and a tank of high test gas and run it through a tank and see how that does.  If the injector is really bad you will end up changing an injector or two.  Take out the plugs and the one that is black is the cylinder that has the bad injector.  The others should be white/gray.  Replace the offending injector and you should be good.