I've been wondering, what could be causes that a high flow cat would break?

 

excessive temperature (usually from running too lean) or running too rich can clog it up as well.

 

any catalytic converter will fail from excess heat most often caused by a rich a/f mixture. what happens is the unburnt fuel gets into the cat and it will ignite. a cat is designed to burn off small amounts of unburned fuel. when there is too much fuel, it gets too hot. in some cases is will get brittle and break apart, other cases it will melt together, hence the term "clogged cat".

 

Ok, cause I currently have a vibrant header and d/p combo and the high flow car went. Luckily they're warrentying it but I kinda wanna figure out why it failed... I mean I'm a 2.4 N/A, and I'm only running a injen CAI and a corsa touring exhaust, and I've never done a tune. I can't see how lite mods like this would make it fail but feel free to correct me if I'm wrong.

 

is the injen CAI the exact same diameter as the stock intake? if not, maybe the MAF readings are being skewed, throwing off your AFR

 

I wanna say yes, I know it's definately no 3" so I wanna say it's a 2.5"