there is a sensor that goes to the egr valve now that it is not hooked up its not getting a reading and in turn throwing off your ecu which is causing it to idle rough. You have to get an egr simulator, I'm not completely sure but I don't think that a resistor with work because the level varies. Look on ebay there maybe something there or look it up in the FSM if the level stays steady then just plug a resistor in.