I have replaced both regulators and do not remember any foam in the area you are noting. Take a look at the pictures in the tech article for more info. I think your glass may just be loose from the pinch clamps. Or the regulator is loose from the door. Does the window open and close correctly?
https://www.pelicanparts.com/techarticles/Boxster_Tech/77-BODY-Window_Regulator/77-BODY-Window_Regulator.htm
Thanks Pelican for all of the tech help.