Ceramic Coating for Turbochargers and Exhaust Manifolds increases both performance and reliability by reducing the amount of heat in the engine bay temperatures and protecting sensitive electrical parts as well as reducing the risk of fuel vaporisation.
There is increased performance too by keeping heat within the manifold and turbo you’re going to accelerate the exhaust gas velocity which reduces back pressure and allows the turbo to spool up quicker, improving throttle response and lag while offering surface temperature
Any surface within the motor that is in contact with another surface while the engine is running will gain an additional benefit with ceramic coatings. An example would include the piston ring to cylinder interface.
A reduction in friction will occur that will increase horsepower by allowing the moving components to operate more freely.
Depending on how many internal engine components are coated horsepower gains can be anywhere as low as a few horsepower to 30+ horsepower.