Ah! Well, that will only make a difference IF your car is sluggish "off the line" right now. What you want to do is remove the little cap on top. Pry out the black seal to reveal the screw. Then use pliers to twist off the metal canister. When removed it will look like the photo below. Loosen the locknut and turn the screw CCW to richen the mixture. Try it in 0.5 or 1.0 turn increments. Most cars will need about 0.5-1.5 turns CCW. If you go too far the car may smoke or not run right due to an over-rich mixture.
CAUTION: This screw was not intended to be adjusted, hence the tamper-proof seal on top. There have been instances where people have adjusted it and it ruined the ALDA. You can't buy a new one from Mercedes - maybe from a Bosch shop, I don't know. Otherwise you would need to scrounge one from a junkyard.
More photos available here:
http://www.meimann.com/images/mercedes/OM603_intake/
Good luck,