Your EGR must be stuck. If you apply vacum and the idle doesn't changed, then either the hot inlet pipe is still plugged, or the egr valve isn't functioning. There is no other choice.
You might consider replacing the hot inlet pipe with a new one. The new pipes extend slightly farther into the intake manifold to prevent it from caking up with carbon deposits. If not, your current pipe will plug up again, although it will take several years.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".