Don't know what to call this part, just know it's not
a hootus

The left side flapper valve on the -6 is very close to
this cover for the u-joint coming out of the firewall.
The air is hot enough that it melted and scorched
the thing.

Has this ever happened before?

Yup. The second one has been fine though. Maybe the first was made of crap. All I know if was a PIA to put in.

Thanks, I wonder what will happen.

"tis only a flesh wound......