The old one (called the "stainless sport exhaust") is the complete, stainless steel system that includes the Y-pipe replacement and has the Dynomax muffler. Doesn't look like Nissan is hawking this kit anymore ( though it is "in stock" at nissanparts.cc )
The new one on Nissan\'s site does not include the Y-pipe, has a "polished aluminum" finish, and supposedly has the variable-capacity muffler shown in this animation but I don't see how that would work since the system shown above has only one outlet just like the stock exhaust.

Brent