I don't recommend any particular oil brand , as long as it 's Benz Spec.. I use Castrol GTX 10/40..
What I will recommend to you on the oil change is to do an archieves search that I posted way back on a TSB -re: oil level change on 104 eng.
They were having trouble with oil fill being too high and the TSB
changes the capacity [ I think it was about 1/2 qt less, but check for sure] ...

I would run this tank and maybe 1/2 of another w/o the FI cleaner and then change the oil, clear all codes [ write down what you have retrieved] and then watch for new ones

The reason I would clear the codes at oil change is you will then be assured of no gas contaminated oil [ which can bring on an Adapt trim limit code]]

At the same time . I would also do the trim memory reset procedure after you get the 1 Flash, no code OK ...
just to get back to Mean values

As far as idle is concerned , the 104 are famous for bad coil to plug connectors under the 3 coils ... if you have not done them, I recommend it , as they are short $$$ and most tech do them at plug change BC of their short life...[$7-8 ea]

The computer stops the injectors from opening when it detects a skip at the plugs, [ to protect the cat from getting raw fuel dumped into it],so these can also cause a lean reading back to the DM,,,
As you can see , all systems are related and affected , one way or another...