A normal catalyst consists of 400 ceramic cells per square inch (cpsi) installed in a rectangular pattern which are enriched with platinum, rhodium and palladium. The harmful gas fumes pass through those cells and are catalyzed into non-harmful. This process diminishes the engines capacity significantly.
A performance catalyst, on the other hand, has exactly the same chemical attributes, but consists of metallic cells with ratio of ≤300 cpsi. Moreover, the cells are installed in a circular pattern, which creates a whirlpool of gas fumes and thus maximizes the free flow of gas fumes through the catalyst.