Hi,
The G-Meter is a feature of the Nismo MFD. You can get them for around $900 off www.nengun.com. Don't think its on the standard meters. If I'm wrong and Vspec 2's have the g-force meter as well, theres instruction on how to trigger the diagnostic screen for the MFD that shows what sensors are operational. PM me your email address and ill send the instructions through. YOu should be able to google it though. Its a pdf file, something like R34 MFd instructions