It never ends...
think you want platinum long tubes). The oxide film
thickness determines the color.
Never trust a man with clean shiny exhaust piping.
Blueing is a sign that you've been driving it proper.
The ceramic coating "should" resist color change
as the color is bound up inside and the outer
surface is more like clear. But they dull up instead.
Black oxide on steel or stainless might be the
most durable against color change, but it also is
high heat emissivity (radiative) and will make the
engine compartment even hotter; stainless bare
is also pretty bad, the silver coated headers
throw the least heat.
The latest thing* in morotcycle exhausts is dual-wall
pipes that resist blueing. The inner can even be mild
steel, the outer is a thinner, pretty-chromed shell
spaced off the main pipe. Nothing wrong with that
but weight and complexity. But it would also help
the heat stay in, and maybe make your O2s work
right. Maybe some day someone will bother... hey,
maybe even the means to get CARB legal long tubes,
if the gas is still hot when it gets to the cats....
* or maybe it's like so last year

