NGK Platinum spark plugs are the OEM plug for the 2003-2006 Nissan 350z. We strongly recommend these plugs for all daily driven 350z's because of their excellent spark and long lasting(60K).
For those 350z's running mildly boosted superchargers or turbo's we recommend going with the cooler PLFR6A-11 plugs.
Nissan Part# 22401-5M015 or PLFR5A-11 = Standard
Nissan Part# 22401-5M016 or PLFR6A-11 = 1 Step Colder
For 350z's running built motors with turbos or superchargers we recommend getting the Iridium plugs