Well luckily this IS a yes/no issue. If the throttle switch isn't closed at idle it needs to be. The adjustment isn't easy and is very seldom necessary. Since it's operation is off or on for your model its easy to test.
The reason it matters is that the computor goes to a fixed state in the off idle position. While in the idle position the controller is trying to control idle speed.
Basically I don't think this is the majic bullet here.
There is a very related issue that can play a big part here. That is the accumulation of carbon on the throttle plate and intake valves. The carbon changes the amount of air the idle controller handles. It also absorbs fuel in different quantities varying the mixture on a tightly controlled system.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician