I have been having a lean misfire with my 98 I30. It usually only happens when I am in idle or low rpm's. Recently my car has been idling a lot lower then it previously did around 4000 in nutural and 6000 in gear. I upped my idle by about 3000 rpms and the problem seems to have stopped but seems to go back down on its own. I have replaced my plugs with originals, coils, o2 sensor and fuel filter. I want to know what is the next best thing to change in the firing order: EGR valve; Mass Air Flow Sensor; Idle Air Control Valve; knock sensor? It is not throwing any codes either. Please help!