Well, the Panzerwagen seem to run better with more petrol being burnt but still not good enough.

Checked at local MB dealer, intake manifold gasket (to head) cost me R40 (~5EUR) each and had to buy'em. Dunno when will I fit them, I am short of time now. Also, just a thought of work required to remove fuel regulator and bits and pieces to reach intake manifold gives me goosebumps.
Haven't checked the spray pattern of injectors when had them removed because didn't know they can cause problems (at that time). All but one looked very clean.
Decided to perform "Italian tuneup" this weekend after it being praised so much here.
Vacuum leaks will be next, I think I read somewhere here that cold-start spraying will reveal a breach of vacuum line by changing the idling speed for the moment after being sprayed.

Engine have light knocking of at least one valve or rocker arm and resolving that is a top priority now.
I will keep informed here what work had made what kind of changes in the engine operation.

Thanks