Where does the oil come from?

[Boxsterivan]

Hi guys!
Not all new here but been away for some time....

My problem:
On a trackday smoke came out due to oil on the right rmanifold! Some 1 litre oil came out in about 25 minutes. There was oil, mostly on the left side of the motor compartment and even on the inside of the rim ..
Filled it up and drove home....

No smoke and no visible oil consumtion on the way home - 150 km. After a night in the garage.... no stains on the floor!
There´s a FVD Brombacher motorsport oil pan mounted this winter.

My questions:
Where can the oil come from?
Can the AOS release that amount of oil?
Can it be that "thing" again?
The summer of 2018 I changed the AOS due to smoke out of the exaust pipes.


Anyone got a clue?

(The car is a Boxster S 2002 with Tiptronic and Michelin Sport Cup2.)