You should be aware of that the hole on top of the air box is for fuel/air mixture adjustment. Although it might have lowered your idle, it might have created a lot of new problems then solved the old ones.

Get a MM (multimeter) and check the lambda voltage, that will tell you where the mixture should be, if the high idle comes back, check for leaks in the vacuum system, most likely cause, then if all checks out, you can lower the idle with the knob on the idle control valve, at least on my 190, there are different versions of the same valve.

xp

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1985 190E 2.3L - a constant project.