Hello and welcome to Just answer.com, Super mechanic here. Please DON’T hit accept until you are completely satisfied with the answer. About your vehicle.
There has been a service bulletin for checking the EGR transducer, which could very well be the problem with it. Here is what it states.
Date: August 1999
Order No.: P-SI-MBUSA-14.20/13
Following are procedures for an EGR vacuum transducer in-car characteristic curve test, internal leak test, and external leak test.
In-car characteristic curve test
The Mercedes-Benz Special Tool vacuum gauge (see below) is used to monitor the vacuum signal of the EGR vacuum transducer while operational in the vehicle. The leak test is performed at 25%, 50%, and 75% duty cycle (DC) using the Hand-Held Tester (HHT). Duty cycle is activated by way of the HHT 'activation' menu (the second screen of # XXXXX "EGR valve").
Internal leak test
External leak test
In Case of Warranty
* see Microfiche for applicable model
That is all the information that I have on it, but wait there may be another expert who has more. I will opt out and open it back up. Please don’t reply to this post as that will lock the question back to me, someone should be along shortly, I’m sure, thanks and sorry I wasn’t able to help with it.