Yep, that would be either High Flow Cats or test pipes.
Like I said, the only ones I have personal experience with on a 370Z are the Berk Technology High Flow Cats and I absolutely love them. I have not one single complaint. I have done before & after dynos and a sound clip video with the stock exhaust and Berk HFCs.
Here is a link to my old group buy thread which has all of the information. The group buy is over now, but PM me if you want to order a set.
DDMotorsports: Berk Tech High Flow Cat/Test Pipe Group Buy!