Yes, I would disconnect the tube both at the EGR valve and at the intake manifold. As Stevebfl has stated, the build-up is always at the opening of the intake manifold.
I cleaned mine out and replaced the egr valve. There was a TSB regarding the old valves sticking, and the part # changed.
My CE light still came on, so I actually replaced the metal tube.
Donnie (Benzmac) has also posted that he no longer reams these pipes out. It takes too much time, I guess, and it is more cost effective to just replace the tube.
BTW, I've always wondered where all that carbon goes if the pipe isn't removed. I guess it just gets sucked into 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".