Hi there! There shouldn't be any problem tuning your G37 with UpRev; however, it is best if you can stop by the shop so we can inspect the ECU part number just to make sure. Worse case scenario, I can do a ECU dump and send to UpRev to crack the code for you free of charge
Let me know if I can be anymore to help. Look forward meeting with you.
P.S Also, we would like to replace or inspect the spark plug before the tune.