Originally Posted by InTheZone

Just buy a HFC

With Test Pipes:
-you won't pass emission inspections, unless you're in one of the states that don't have them
-your car will be spitting a ton more carbon monoxide=bad for everything
-if you're ever idle and smell something bad, that's your exhaust

a HFC will give you almost the exact results in HP gain, although neither gives you much. But it still functions like a normal catalytic converter