I'll jump in and argue with neither of you......
IF exhaust wrap is used on VW Vanagon header pipes, they are likely to
disintegrate from the inside out anywhere along the pipe including near the
head (ask me how I know).  I believe it's due to the mild steel used in
these pipes not compatible with the heat kept into them by the wrap,
although I don't know the chemistry here nor do I know the content of
possible rust inside these pipes prior to installation.  Anyway, if you have
this stuff or are contemplating, please check archives for exhaust (yeah,
it's in there somewhere) and see Lilley's suggestion on using the wrap, then
read what others have experienced.
Personally, I will try the POR-15 on the exhaust and post the results over
the next year.  I will also use my remanufacturing facility (sure is handy)
to properly clean the pipes prior to the POR and follow instructions.

JB
'89 Wolfsburg MV

>I really hate to argue with a Chem Prof... but Matthew, what goes first in
>an exhaust system? The tailpipe... then the muffler. The last thing to rust
>out is the down or crossover pipe. They may crack (bad motor mounts), but
>very seldom rust out.

>Has to do with amount of moisture left in them. Hot means dry.

>tim in san jose (where nuttin' rusts out)

 >>hot stuff rusts faster. ever take a thermodynamics class? hot=more
energy.
>>more energy=faster reactions. faster reaction=more rxn in same time
>>period. more reactions=rust forms faster under same conditions. ions
>>(salt) and another competing pathway to products.
>>-matthew
>>
>>Matthew Pollard          "Racing with the wind and flirting with death
>>Dept. Of Chemistry        So have a cup of coffee and catch your breath"
>>University of Idaho
>>www.uidaho.edu/~poll7356