Is that why I've seen a few hood pads with a little square-shaped section of shiny metal or foil pasted on? I have been wondering about that.

That's a modification equal to my skill set--cutting and pasting! All kidding aside, anything I can do to extend the life of my AC interests me. I had two compressors replaced in my old 300D and it was far from cheap.

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Current car:
1982 300D A New Hope! Three-plus tons of China blue steel, rubber, and magic.

Past cars:
1985 300D, Glorious anthracite on black. Gracie. (R.I.P.)
The rest were crappy--including a 1970 Orange Gremlin.

no. the foil on the hood pad is to protect the paint on your hood from the turbo in models that the turbo is uncovered! I think the 85D california version, and the 86 and up 300D's need it.
A New Hope, will not need a foil hood pad. the air filter provides all the radiant barrier you need.
I don't know if the OEM had insulation on the pipe. I think it's an add on that owners/technicians later installed in an attempt to improve the cooling of their cars. I'm fairly certain that all the old photo's I've seen of the cars had no insulation on that pipe.

I thought it was for the trap-ox mounted close to the hood on those models.

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Gone to the dark side

- Jeff

yeah, all the exhaust items if they don't have a shield they'll damage the pad and the paint on the hood.