high flow cat question

[Tzar177]

Should i go with a ceramic or metal core? The metal core one says "for offroad use only" but also says 40% better exhaust flow compared to the ceramic and cost double. Would there be a sound difference between the 2? Would they both past emmisions tests?

[zoomin MP3]

Any time an aftermarket part says "for offroad use only" it means it's not street legal, or DOT approved. So the metal core probably does flow better because it won't pass emissions. There's a metal crosshatch inside your cat that converts the exhaust gasses. This crosshatch has to be tight enough to conver the right amount of exhaust without being too restricting. The metal core probably has more spacing in the crosshatch, thus producing a "high-flow" cat, but could possibly fail emissions.