What adjuster does this hole lead to?
 

In the top of the air filter cover there is a hole. When I remove the entire air filter assembly, I can see that the hole leads to a metric allen screw sized 3mm. I didn't touch it as it appears to adjust something in the fuel injection system. I just inserted allen keys until I found the size. So, what does this thing adjust?

Duh, I should also have said my car is a 1988 300SE. Many of life's mishaps are caused by hitting the "send" button too quickly!

Ron,

Thats the Air/fuel mixture adjustment screw

Ron,
That is the lambda tower. It is used to adjust the air/fuel ratio.
Best bet...leave it where it is. If the mixture is off, its probably something else.
Brian

I thought it would be something different because I saw my mechanic using what looked like a long screwdriver to turn the screw while he had a "Fluke" meter attached to some of the "pins" or whatever you call those things under that screw-off cover on the driver's side firewall. It has 6 or so female pin receptacles under the screw-off cap.

Is that how you adjust the air/fuel mixture? I'd have thought you'd have to have an exhaust gas analyzer to do it?

Ron,

I am sure someone will correct me if I am wrong. I beleive the air/fuel mixture is adjusted by the ECU the adjustment screw is used only if it gets way outta wack..:)