ceramic coated are great"because the coating acts as an insulator, it keeps heat inside the headers and out of the engine compartment, where lower temperatures permit [denser] fuel/air charges to reach combustion chambers. At the same time, demand from power-robbing accessories is reduced. Also, by retaining heat within headers and smoothing header bores, the coating increases the velocity and reduces the turbulence of exhaust gases, leading to more effective scavenging of cylinders."