Those German engine mechanics could not hold a gasket aligned and in place while bolting the covers. it kept falling off, so being brilliant as they are they used a sealant gasket instead.

{Joking ... cause honestly I dont know}
That oil on top must get hot and smell bad, I would also suspect the cover seal as you do, but isn't the AOS Oil seperator plumbing near that area as well? I would suspect that as well as I have read that sometimes the connections don't seal well and it could leak.
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"It broke because it wants to be Upgraded

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2012 Porsche Performance Driving School - SanDiego region
2001 Boxster S, Top Speed muffler, (Fred's) Mini Morimotto Projectors, Tarret UDP,
Short Shifter, Touch Screen Dual Din Radio, 03 4 Bow glass Top (DD & Auto-X since May 17,2012)