Toyota 4A-FE pushing oil to distributor cap with high revs/acceleration
 

Anyone had similar problems with their car?
My Avensis does not like high revs or acceleration. Gets oil into the distributor cap, and because if this, runs with 3 cylinders for a while.

Where to start troubleshooting? Could it be a ventilation problem of the valve covers "breathing hose" ? I suppose with a bad oil seal on the distributor axle, oil would leak all the time.

Small update, checked the pcv-valve and connecting hose, both ok.

Clean the engine bay and do a test drive to see where it is coming from?

From the distributor shaft seal. I was overtaking a car once and in the middle, pa-chaff! Engine coughed and ran with three cylinders. I checked the distributor cap first only to discover it to be very oily from the inside.
Cleaned the cap, ran perfectly again.

It's around 4000 rpms where this happens. This is also where the best power would be.