Carbon Monoxide
Mild CO poisoning from car exhaust sets my ears, and in particular,my earlobes on fire.They turn red and are physically hotter than the surrounding area. Then I get a headache. Then I get sleepy.Sometimes my mouth tastes like blood.When my ears get hot, a mirror-check usually shows that my face is also red.
My ear lobes will remain hot for quite a while after getting clean air.Perhaps an hour or more. My brain alerts me to the heat in my ears. The physical touch proves it.Then I get out.(I hate those headaches.They're worse than the too-much-sun/hard work,ones)
My 68 Barracuda has lots of places where air can get in. Lots and lots. My cowl seal is good. My headers leak a little at the merge point,only. The pipes are 100%. The turndowns exit about flush with the outer edge of the bumper. There are 3 holes of 1/8th, drilled in low spots in each side, including 1 in each of the mufflers...........I have no CO issues at all.
And if anybody cares; I have a thermostatic clutch on my shrouded 7-blade fan. It can push a lot of air. And I'm geared for 2200 @ 60mph. And an early style rear spoiler. And lots of holes or faulty weather-strips.