Find the vacuum modulator for the egr valve, it should have a white and a yellow hose going to it, pull the hoses off of the modulator and touch their ends together so you supply vacuum to the valve. If the valve is fuctioning and all passages are clear then the idle should stumble, unless you have a valve that is sticking open (never seen that one) or the yellow and white lines are swapped on the modulator the chances of the egr valve causing your stalling problem are slim to none. If I had to take a blind guess I would suspect something with the idle air control motor or the cap, rotor, and wires first.