I think you will see performance loss if its clogged or something that is hindering it from performing. It sound like your internal is just mess up but air flow isn't restricted. That sucks that they don't guarantee the new one. I would speak to Nissan USA. I also wanted to restate that it MIGHT suck back debris. It has happened but dont want to scare you into spending money.
As for the brakes you can do it yourself. Probably take a good 1 or 2. There is a how to in the how to section.
Pops, are you going with the Cajun b pipe+ cat? IIRC you have the jba shorties?
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