just my opinion but I doubt nissan has any idea whether your vehicle was originally equipped with the secondary cats or resonators. I am starting to doubt whether they know why some has cats and some have resonators
. I removed my resonators and have been told by service manager as long as I dont fool with cats, I am okay. I was very pleased with performance gain by opening everything up after cats.
Here is a thread on my exhaust:
A new exhaust configuration!!