[olddog]

In terms of performance, it is best to not let the exhaust gasses cool, because pipe velocity drops when the gasses cool. Black absorbs heat. Shiny, reflective surfaces reject heat. Therefore a silver coating on the inside of the pipes would be better than black, from a performance perspective.

Although this is true, I wouldn't expect a huge power difference. A race team, looking for every last pony, may do this if the rules allow. Maybe someone has ran a dyno with and without coated pipes and can speak to the difference.

I'm not saying this is going to matter, however silver is theoretically a step in the right direction.