If you're talking about G-Power, I'm not sure they make the kit anymore. If they do, it's a good option. My G-Power kit on my Z4M puts out a lot more midrange than other kits that run similar max boost levels. I see peak boost from 6k rpm to the 8k rpm redline.
Here is another video, and it's all I'll have until the end of the month:
G Power Z4M
and VF Engineering Z4 3.0i