Well, I bought some exhaust wrap, but not to wrap my exhaust, mind you.  I
needed to shield some not-so-hot parts from the hotter-than-H parts.  I've
read reports of exhaust headers rusting very quickly after application of
fiberglass exhaust wrap.  Why?  The stuff soaks up water like a sponge and
holds it.  Yes, I just tested it.  So you can imagine what happens over
night when the dew point drops, no?  Yes.  The doom of all bare steel,
moisture, gets sucked up against the headers.

It seems that sealing it against moisture would be the correct way to apply
the stuff, which can be done by applying the appropriate and expensive
sealant.

No problem for stainless steel headers, right?  Maybe not so, since the wrap
causes the temperature of the headers go up, which may be too much of heat
stress for the metal to handle.  And that might be another DEEP, DARK secret
in itself.

Chris S.