We've confirmed these cats to be the latest 200 cell HJS units by the serial tag. The chance that they are actually damaged is very, very slim. UPS would have had to run over them with a truck to damage them internally during shipping, and there would be obvious external signs of that.
Plus, no cat codes or CEL are present.
We have installed countless of these cats in house, in combination with all sorts of other headers and mufflers, and have yet to hear what may be referred to as a rattling noise during operation. However, anything is possible given how freer flowing our cats are and how that may "excite" some of the baffling in the OE mufflers, producing a momentary harmonic. Without an actual sound bite, we are doing our best to help.
Nexus, we're not looking to upsell you, but if you are indeed looking to upgrade your mufflers, let's see what we can do for you.