I'm in a hotel in Atlanta right now, so I don't have my car in front of me, but the egr valve is at the rear of the passenger side of the engine.
It looks like sort of a flying saucer. It is reachable from the top of the engine.
It has a small diameter metal tube that exits the back of the egr valve, and goes around the back of the engine, between the engine and the firewall, and ends at the intake manifold.
You can ream it out with a cable attached to a drill motor, or simply replace the tube. Benzmac has posted that he usually just replaces the metal tube.
BTW, the blockage is usually right where the metal tube enters the intake manifold.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".