Your engine does not have an idle control valve. M103 and M102 engines have idle control valves.
M104 engines have a throttle actuator, which electronically controls three functions: Idle speed control, electronic accelerator, and cruise control. I don't believe it can be cleaned to fix the problem.
I don't know if the problem is your throttle actuator or not, but if replacing the Mass Air Meter didn't fix the problem, and if you don't have a vacum leak, then I would point the blame at the throttle actuator.
They usually fail for two reasons:
1. they have potentiometers that wear out over time.
2. they have a wire harness that has bad insualtion which flakes off, which cause the actuator itself to malfunction.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".