Like many M104 owners, I too spent a not insignificant portion of my too-short life cleaning the EGR pipe. As I stood there hunched over, back in pain, fingers filthy, sweat beads trickling down my cheeks, it occurred to me that this was most likely a colossal waste of time.
Why? Because a clogged EGR pipe is the best thing that can happen to a motor, next to the EPA having never been formed to begin with. A clogged pipe may cause you to fail an emissions inspection, but a better solution for that would be to move to another state.
Unless you have a rough idle caused by an EGR valve being stuck OPEN, which you can test with a Mity-Vac at the EGR valve, then you can rule out the EGR.
Am I wrong? If so, please calibrate me.