Many guys have their headers coated withthe same silver ceramic coating that have their sidepipes coated with. I don't know if silver vs. black has any substantial impact on the underhood temperature; but I have heard from some of the guys that coating the headers silver can present a problem with staining. I have that if
oil leaks onto a hot silver coated header it can stain and spot the finish. I just spoke with Scott at Airborn Coatings (Bob, thanks for the lead) and he said that any staining or spotting can be buffed out.
Tony