head port help

This type thing seems to surface about ever 10 or so years. I remember in the mid 70s when they had a carb base gasket with a screen for mileage and power. I not going to say they don't work because I have never tried them. But how well does air flow thru your house with and with out screens on the windows, it flows better without the screens. Logic would seem that the screen slows the airflow and I thought higher velocity airflow is what we wanted because fuel droplets fall out of suspension as velocity slows. BJR Racing am I close or way off base? From what I read you know quite a bit about cylinder heads, flow and velocity.
What are the screens made of poly or some type of metal? What happens if you engine swallows a piece of metal screen.