I wasn't aware Mercedes put carbs on 190 models, but if you have a flat spot on acceleration and the car idles smooth it could be your fuel filter possibly, or the accelater pump on the carb. Depending on the type of carb you have the pump may need to be replaced as part of a total rebuild or the pump action can be adjusted. There is also a posibility that the carb may be jetted too lean.
Then again it may not be a carb problem at all. There could be resistence in the ignition wiring or a coil that is going bad that will give you "carb" problems.
1990 190E 2.6
1996 Grand Voyager 3.3
1985 Mustang GT 5.0 5 SPD
1982 Suzuki GS 750T