This is a useless feature.

In every single M52, M54 engines I have had...I removed the cosmetic covers and sell them on ebay for ~ $35/each.

Now I only have the oil filler cap in place.
The ignition coils are exposed, making it much easier to inspect and wipe off spilled oil. Also, by removing the cosmetic cover, the coils are not trapped in a heated environment.

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1998 E39 528i 5sp MT
2006 E53 X5 3.0 6sp MT