What Steve means is that Mercedes don't have belts, they have chains, which per Mercedes have no replacement interval, although there is many opinions on actually going ahead and replacing them anyways. Failure is quite rare of these chains, with a few exceptions, and your 119 engine is not one of them.
I have heard the throttle motor assembly called several names. Unfortunately they were both mentioned in your list, Arif, both gas actuator and intake slide. I wonder if one of them was an incorrect part and should have been deleted? Maybe Phil at PartsShop can help identify these part numbers.