"Blow-By" on a 2009 Toyota Camry create Oil Leak that is located on top of engine

I am in the process of purchasing a 2009 Toyota Camry. Unfortunately, oil has been discovered on top of my engine a month after I bought the car. It is my opinion this is not a new leak.
1) PVC Valve and Oil Filler Cap are both replaced, problem still exists.

So, I drove from Fort Walton Beach to San Antonio Texas, and I only lost 1/4qt
of oil. It looks like most of it is sitting on top of my Exhaust Shield, and the drivers side of the engine. There is does not appear to be a big leak on the bottom, only residual from the leak I am describing. So once settled, it stops.
The Leak only appears when I drive fast, as on the Freeway. Under 40mph, I don’t see any kind of a leak. (I’ve washed the engine hoping to see some sort of seepage but no luck)
Myself, and 2 other mechanics have gone over the entire engine and we can’t find where the leak is coming from.
Could this be “Blow-By” from using low quality oil, or infrequent oil changes? Where is it coming from? Ideas anyone. It is driving me NUTS.
THANKS
arte