M103.. may be a really dumb question....
 

On my 190E / M103 air filter housing there is an un-used hole near the center with a rubber grommet in it. Is something supposed to go there?, I've looked at several other 2.6's and none seem to have anything there.

I put a piece of duct tape over it as it is a straight shot from that hole into the intake (inside the filter perimeter) and the engine ran "differently" , so I took the tape off (engine seemed to run better) and it seems that there is just a little bit of pressure blowing out the hole. Is it supposed to "balance" the intake airflow, or something like that?

I could not find any reference on the CD or in the Haynes manual.

Thanks in advance.

That's where the tool goes to adjust the lambda.

Thanks Brewtoo,
So to clarify, If I'm not adjusting the lambda, it should remain open, or un-plugged?

Yes, it is intended to be just as you described. Open with a rubber grommet.

If putting duct tape on the hole effected the way the engine ran, then that suggests something is amiss. The fact that you're experiencing pressure there is odd. The gromet should seal the hole from the intake -- and if the gromet were to lose its seal, you should experience vacuum, not pressure.:confused:

It was very slight pressure, it felt like a very, very weak human pulse. I would rather see a tiny bit of pressure, than un-filtered air being sucked in. The car runs great, nice even idle and smooth power up to 6K rpm. It seemed to miss, slightly with the tape on it.

Take the whole air cleaner assembly off, and you'll be able to see how it seals. If it's sealed properly, then you're all set. If it's not sealed properly, your intake is ingesting unfiltered air.

Well, if this was a dumb question, then I have an even dumber one. What's the "lambda?"

Not a dumb question at all. It simply is adjusting the fuel/air ratio.

If you do a search you will find tons of info.

Okay, I've always heard that referred to as the "air/fuel ratio adjustment screw," that's all. Thanks.