The idle is adjustable on your car. Try adjusting the large screw at the front lower of intake out (counter-clockwise).
A problem that occurs on these engines is that they have a thermostatically closed additional air valve. As they fail they need to be fully hot to close off all the way. The device should close completely by 130-150deg F (not sure of exact range, but it should be closed well before engine thermostat temp). If the device is still partially open at the t-stat temp and the idle is set there then the idle is too low when it finishes closing.
Bosch Master, ASE Master, L1
33 years MB technician