190E 2.3 mixture adjustment

[ssanmor]

Hello.
I have just bought a 190E 2.3 8valve (1992). The previous owner had the fuel system readjusted as the idle was low and sometimes it stalled. Then the idle went up to 1000rpm and the car run much better. However, it didn't pass the emissions check and had to lower it again, so now it stalls sometime and doesn't run as it should.
I want to increase it a bit. He told me about a kind of adjustment with several positions, although the fuel distributor hex. screw sound more likely to me.

Can I do it myself (I have an oscilloscope and can check the duty cycle signal or whatever in the diagnosis conector if you explain me how to do it).

Is there any other adjustment in this car?

Best regards.