Anyone remember radiator blinds?

More to the point my Roadster keeps a steady 90 but of late, as the ambient temperature has dropped the heater struggles to keep me warm above 70mph. It seems as if too much cold air is getting into the heater. So I may blank off part of the intake for the winter.


Peter,
66, 2016 Porsche Boxster S
No longer driving Tarka, the 2014 Plus 8...