I have my Z back in possession. None of the technicians could hear the noise on a 40mi test drive. They ended up doing the right thing and took care of the customer, me. The service manager is going to replace the part under warranty. He is giving me the benefit of the doubt. The dealer will be installing the part when it comes in some time next week.
On a different note... they informed me they have a new GTR waiting for me in the show room for me to buy.
I'm happy with my Z.