Rattle and Hum....

[ImBuggin]

I have an '01 2.0 and there is a distinct noise coming from the first box in the exhaust. At startup and around 2,000 rpm, it rattles incessantly. I crawled underneath, shook the exhaust, and it still rattles if I bang on it. What part of the catalytic is this and if I buy a cat back system, will I bypass this stupid box? I see most cat back systems have only a muffler and a catalytic (which looks more like the second box). I can’t tell, but the first box looks like it is connected to a set of downtubes, but the pictures with the install of the 3” pipe shows them removing it from a “flex” hose. What’s the deal if I replace it with an aftermarket and will I still have this stupid box?