A search found this:
http://www.xmission.com/~dempsey/perform/nospike.htm
I haven't digested it yet and leave that to you.
I don't have direct experience with the E300D but I recently had an interesting problem in my W124 OM603 engine which was related to the wastegate.
After a lot of $$ and effort was put into restoring the engine(rebuilding the top end) my car still ran poorly. It had new lifters, a reconditioned head, new IP seals, timing chain etc (the car had received basically zero maintenance other than oil changes for 250 K miles - IMHO a testament to great reliability!)
I was afraid the turbo was bad because boost was low. It was about to be sent to be rebuilt when I discovered the flapper was sticking in carbon buildup in the wastegate. The actuator was only partially operable and never completely closed. Perhaps you have a similar problem?
DDH