Ceramic coating is very expensive, as it needs specialised equipment for spraying the ceramic material, I doubt it any HK base garage nor modification shop has this type of industrial strength equipment.
Only if your existing 20vt cast iron exhaust manifold has cracked between no. 4 & 5, otherwise there is no need to change. On the other hand, this16vt aftermarket design is an equal length one, so it will benefit the air flow to the turbine.
