Think of exhaust gases as a piston moving down through the tubular system. As each pulse travels down the system, it creates a vacuum behind itself. The negative pressure behind each is the scavenging effect.
As the velocity of the pulse increase, the negative pressures also increase. As you increase in velocity, the length of time that gives you a negative pressure in the system is increased.
The net result of high velocity to assist in scavenging is increased performance of the intake and exhaust system. Maintaining higher exhaust temperatures throughout the system increases the performance in many ways.
Think of exhaust gases as a heavy liquid such as an oil additive. If the liquid were traveling down a tubular system in a cold state, it would move very slowly. But if you heat the liquid, the density of the fluid changes and the liquid responds to the heat by increasing its velocity.
Exhaust gases respond in the same manner. Higher temperatures in a system increase the flow of the system. If the liquid is allowed to cool in the system, it slows the flow of the liquid.
By this illustration, you can now see the importance of maintaining higher temperatures in an exhaust system.
Ceramic coating the manifolds and crossover helps to maintain exhaust gas heat within the system. This translates into more exhaust flow due to maintaining exhaust temperatures as it flows out of the engine. By improving the scavenging of spent gases, the engine breathes more efficiently. This reduces contamination of gases, thus allowing the engine to develop more power.
By keeping the heat in the exhaust you will reduce under hood temps. This keeps you engine running cooler and the intake air charge denser. Cooler inlet air translates into more HP and reduced detonation.