Guys confused But you can either try another smog shop or point him to the Factory Service Manual.
http://www.nicoclub.com/FSM/370Z/Coupe/2013/EX.pdf
The manual is for 2009- 2014
2009 - 2014 Nissan Service Manual
TWC(2) are the Cats so there are only 2 NOT 4
Have him call the service dept at a local Nissan dealer to further convince him.