EGR cooling?

I don't think you'll get anywhere trying to improve the ignition. Your HC and CO are way up from previous tests and your NOx is way down, which suggests you're running rich. I doubt it's from a fuel pump fault -- could be a carb calibration or adjustment fault or a sticking choke or other air restriction. HC is unburned fuel; CO is incomplete combustion. NOx happens when combustion chamber temperatures rise high for whatever reason, particularly with a lean mixture. Rich mixtures burn cold and there's no excess O2 to combine with nitrogen, so NOx doesn't form.

With this new info, I'm changing my vote: it is still somewhere between "quite possible" and "quite likely" that your cat (meow!) is past due for replacement, but it also looks like you've got a running condition to correct before doing so, or else the new cat (meow!) will be killed to death.

Pull a spark plug or two — what do the firing ends look like?

Did the NOS carb get installed between the previous (easy pass) test and the recent (multi-flunk) test?