I wsa on www.mbz.org
the other day and and found a trick for messing with the EGR. Lookk at www.mbz.org/resources/articles/engine/killegr.html
They have a disclaimer that says this is tampering with the emissions system and is illegal for road use, but they say it will increase performance and mileage and is great for off-road racing. The tip is specific for the M617 turbodiesel motor.