If your EGR is working properly and seals tightly, the BB trick is great. Better yet remove all the vacuum plumbing associated & clean up the engine compartment. The "stage 2" mod involves making a thin blockoff plate you sandwich between gaskets under the EGR for a more positive block. The final solution ("stage 3") is to totally remove the EGR and fabricate a blank plate to cover the intake & exhaust openings! Photos are here:

http://www.meimann.com/images/mercedes/OM603_intake/

Mine was leaking so I went for Stage 3.

Note that this IS NOT possible for most 1990-1995 turbo diesels, which require electronic tomfoolery so as not to make the computer unhappy and take away your horsepower. It can still be done but it's much more complicated. The turbos up through 1989 have no such trickery.