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.

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1993 190E 2.6 135k
1989 Ford Thunderbird SC 5 Spd 79K