4runner

I have a 2000 4runner with TRD headers. I am supercharged and have done all of the fuel mods. According to all of the ceramic coating shops, adding a coating can increase horsepower by about 15. That is a significant amount, so I was just wondering if this is actually accurate. If so, I will probably end up taking off my headers and re-installing them. I have also thought about using header jackets. They fit loosely around the headers and can be installed with the headers still on the truck. If moisture buildup is what causes damage to the headers after a year or so, then I'm thinking the jackets would be okay since the airspace between the header and the jacket could help with evaporation.
Any help is appreciated.
-Neil