NGK DILKAR8A8 is your best bet for a boosted car. Those are the OEM GT-R plug and we have had great success switching to those in our boosted z's. A much more appropriate gap right out of the box.
For a N/A car just stick with the OEM plugs which should be a NGK DILKAR7B11 or Denso FXE24HR-11. The Denso 24 is more like an NGK 8 when it comes to heat range. The hotter plug might make more power on your N/A car but it will put you closer to detonation.
NGK is the way the go for boosted cars using the GT-R plug. If I was going to keep it N/A I would just rock the true OEM Denso FXE24HR-11.
Thanks,
Alex Goodwin
AlexG@motionlabtuning.com