[PhaseP]

The vapor coming out of oil fil cap or the breather line from valve cover is the blow-by gases and expected. I can't tell if it is a lot or normal in your case. If you are getting vapor out of the valve cover breather tube it means your PCV is not stuck closed.

Is it possible some part of the valve cover gasket got rolled and pinched at a point during installation and so not sealing well? It is not uncommon. I would check with a inspection mirror all around