Exhaust driven cooling airflow? It's a rocket bell. I saw a b&w pic out of an old Popular Mechanix Illustrated from the 50s that had a Porsche race car with a similar system.
My own design uses cooling air into a Coanda nozzle.
If it was cut down to what's behind the tail lights and inject air at the leading edge, it would mimic the Jetoptera design. Plus there would be a sight-line for the rear view.