[Greg Reimer 7376]

Stainless steel doesn't absorb heat along its surfaces. It reflects it.Chrome moly or mild steel absorbs heat as the exhaust travels along its length.Seems to me that the exhaust temperature leaving the collector would have to be hotter than the other material headers. All of your wives probably have Revere Ware stainless cookware. The reason the base of the pots and pans have a copper coating bonded to it is so that heat absorption will occur, otherwise food wouldn't cook very well. The heat from the flame would just go around the pot on its way up. 80 or so years ago, railroad mechanical engineers, always looking for more efficiency,tried building a steam locomotive boiler with stainless flues,in an attempt to cut down on rust, frequent maintenance, and constant boiler flue replacement. That engine steamed so poorly that it couldn't get out of its own way, so seamless steel tubing went right back in. I also would surmise that under hood temperatures on cars with stainless headers would be lower due to the same factor.