I had an auto Rabbit (or two) back in the 80's... never again. I fabbed an air duct from the grille to under the heat shield. A fan would be a good addition.Most of the heat from the exhaust is radiant, so a reflective heatshield is pretty effective. If I were to add insulation, I'd put a thin layer on the starter side of the heatshield, leaving room for cooling airflow.