With my 850 (10 valves) I understand that there's no way I could
adjust the idling device (or non in 10 valves model) as in 20 valves. Sometimes ,I felt there is some erractic idling while at traffic lights.

Is that normal?

Is this a common problem for 850? Seems to be, especially in my country
I was even told it is. Why is that so?

It may be a simple one but can anyone tell me the problem?
Can it be the alternator? I am driving a 850.