This may sound stupid- but did you check your nismo for spring spacers on the front?
When Nissan ships 370z Nismo models it puts hard rubber spacers in the front springs to keep the front lip/facia from scraping on the ground. This is unique to Nismo's because of the extension vs the sport model. There have been a LOT of dealerships that forgot to remove some or all of the spacers upon delivery. You might want to check this before putting new springs on.
ATTENTION All Nismo 370Z Owners! Check this thread first before driving your Nismo! - Nismo 350Z / Nismo 370Z Enthusiast Community
^these things