A catalytic converter from my understanding works off of heat. If you put it in the exhaust it kind of gets pointless to have one. Manufacturers put it near the exhaust manifold or right into the Y Pipes so they cat can heat up quickly and bring emissions down on a cold start and so it can work at optimum efficiency. Once the exhaust fumes hit your actual exhaust they're not all that hot anymore. I see if you're gonna runu a race header just run it without a cat and then take it off for emissions....I mean its once every two years...it's not that hard. Or go with teh SVT setup like I mentioned before.However i gaurantee the temperature difference will not cause you to fail emissions testing unless you put it like all the way back. Even if it does fail (how?) you will just have to bolt the old crap back up once a year and thats it.