When the car is at idle the engine nearly dies and sometimes does. It drives fine but idles slow when at a stop. Any suggestions? I get a code saying MAF(P)? and/ or EGR valve not closing/opening properly. Which could it be?

MAF = Mass Air Flow sensor.....get it checked.
EGR = Emissions control valve.....get it checked.

-You people really need to start posting what kind of car and engine you have. As there are multiple generations, and multiple engines within the generations...