As I said before, I'm not familiar with the specific carburetor your car has. The enrichening system, sometimes called a power valve or economizer valve, can be built in several ways. It will probably consist of a diaphragm that is vacuam actuated (to be precise it is actuated by the lack of vacuam causing it to enrichen the mixture). There is at least one carburetor that I know of that uses a piston and spring in a bore instead of a diaphragm.
You need a good manual on that specific carburetor and/or do some exploratory surgery. If you have never really messed with carburetors, you may want to enlist a good fuel system mechanic for the job.
I read one time that carburetor was a french word that meant "don't screw with it".
Have you checked to see that the accelerator pump is squirting fuel when snapping the throttle open?
'84 Euro 240D, 516K miles
'88 300E 5 Speed
Over 800,000 miles in