Dan,
My thinking is the extra height verses the stock valve cover height for more air circulation, etc.
There is just allot more room under the chrome valve covers. My old one had a step down at the rear which really reduced air flow plus the internal baffle lowers the height even more limiting circulation.
Using the Stant unit you suggested for the Mopar PVC works great! It does not suck up too much oil vapor. On the front I am using the tall K&N air filter for the inlet.
Because of the extra height that airflow and circulation helps keep it a little cooler as well. I have had the cover off several times to try different valve lash settings and the oil does not accumulate or cook on the chrome valve cover like stock units. Maybe the oil vapor has a chance to cool a little more because of the taller height?
What ever the reason, whether height, air circulation, air flow, cooler temps or the combination of all the above your suggestions work great!
