Thank you for the replies.
Currently I have the CD Manual from MBZ and also using the index files from Steve Nervig.
http://web.mac.com/dakota/Mercedes/Indexes.html
Btw, if you do not have the index, it is priceless.. a better way to navigate the electronic manual (specially for us new DIY). Plus additional resources.
He has included a fault code manual and while reading it, in page #8 I noticed the following paragraph.
This paragraph appears at the bottom of the page, topic being (Check Engine Light (MIL) Diagnosis.
Under subtopic Mixture Adaptation:
The engine control module automatically performs a mixture adjustment. The degree of correction is calculated constantly and stored in KAM (Keep Alive Memory) RAM. The self-adaptation is performed at idle and under partial load. Maximum correction towards rich or lean is 25%. After reapir work is performed, the engine control module will automatically adapt itself again after approx. 10 trips. After eliminating a malfunction or after trial installation of an engine control module from another vehicle, the self-adaptation feature must be reset to its mean value.
(This is not where I originally read the info - interesting that I found it here again).
I have another issue that has appeared off/on over the last half year.
I will create a separate post for that.