Ceramic coating on ANY header will reduce radiant heat transfer. The point is, you for mild builds (less than 300HP -- WHERE THE POSTER IS), the bigger shorties won't help at all. Long tubes WILL help the bottom end.
I believe I have both copies of my dyno runs if you really don't believe what I'm telling you happened on my car. Search the threads - you'll find many other cases of folks who didn't pick up anything on mild builds by replacing the HO headers with bigger shorties. Can't imagine why I'd mis-lead about spending all that money to brag about a loss in power. (grin)
Ambient temp. was about 45F on both runs; same dyno, same operator, different strap down session. The only changes where addition of FRPP shorties (ceramic coated), and I took my usual dino oil out and put in 5qts. of Amsoil synthetic. At peak we dropped from 225 rwHP to 222HP. There was no gain at any point in the pulls (from about 1800-5500), and the loss was greatest at peak. WHen you consider the error/variance of a normal dyno, what you can conclude is that the bigger shorties made no difference at all. As stated before, for stock/mild combos, DESPITE their appearance, the stock headers are not flow limiting.