Installing the Utec on the Z is easy. Instructions are very straight forward. For the G35, it's totally different. I had a hell of a time installing it in my G35.
However, you'd need to get it properly tuned, immediately.
I have YET to see a shop that can tune the 350z/G35 UTEC properly beside Forged Performance in Marietta.
DO NOT EVER pull and use those MAPS online. After installed it, run MAP 0, and MAP 0 only your car and try to get it tuned.
MAP 0 - even though they said it's a straight bypass to the ECU, it's not really. It still changed your ECU parameters.
Tuning the VQ is very tricky. All cars are different. Even if you have exact same mods (same brands, etc.) both parameters will be dramatically different.
DO NOT ever try to use other's map. I've seen couple VQ blew that way, NA. lol.
If you haven't got the UTEC yet. I sway wait a little. New stuffs are coming out so it's may be better for your car.
Btw, do you need a UTEC? What mods do you have?
If you need help, shoot me a msg on AIM.