As I posted before, just disconnect the hose that goes from the modulator to the EGR valve. Apply some vaccuum and see if it makes your engine sputter while idling. If so, your EGR is probably fine. If not, you might want to clean the EGR valve. Also, you can push the EGR valve up from the bottom through the 1/4" or so holes. BUT, you could ruin your EGR diaphram doing this and then you really will have to buy a new one, so I would just try applying vacuum.

Finally, you probably already know this, but the modulator is the small, round plastic thing with two hoses going in and one going out (to the EGR valve). The EGR valve is the round metal thing with a metal tube going to the exhaust manifold, another metal tube going to the intake, and vac hose going to the top of the round metal thing.