New 3" exhaust with 2.5" Tailpipes

Someone did do a test using an Infrared thermometer from the header tubes to the tailpipe. Wish I could remember the numbers but there is a dramatic drop in temperature (and density) by the time the exhaust gases reach the tailpipes. You can't touch a header tube, but you can touch a tailpipe without getting burned. I'll have to find that article, or better yet, do that test myself.