Cats are more efficient when theyre hotter..technically. Ive coated and wrapped my dump... Initially Id wrapped it.. under bonnet heat was cut dramatically. Then dump was off with a turbo upgrade, decided to get exhaust manifold, turbo exhaust housing and dump heat coated,,, All back together and noticed more heat under the bonnet and there was no way you could touch any of it without taking acouple of layers of skin off.. Re-wrapped the dump and temps went down again. Repeated pulls on the dyno and you can hold the dump... That's got to be good in my book Heat re-tension is energy kept in the system basically.. scavenging and exhaust speed..