I'm not a tuner or racer by any means, but it seems to me that the design Mazda used for the exhast system was not the best. And I say this not so much from a perfomance perspective, but also with regards to potential reliability issues. Is it correct that the 6 has for catalytic converters? Is this typical for similar sedans? Wouldn't the use of a properly designed header system eliminate one or two of these? I've heard stories of engines failing due to clogged cats.

 

This is correct on both accounts. There are precats in the headders and then two more in the exhaust after that. There are currently 3 companies that make headders for the 6s
CPe- the most expensive, but also the best quality and get's the biggest gains
MSDS - middle of the road price, decent build quality, and decent gains
OBX - there have been some problems with the fitment of these and issues with poor welds causing leaks, but they are cheap, and they do work....when they don't leak.

-Cameron Keffer