[GuidoK]

Are you going to install it yourself?
When I was shopping for a system (1,5 year ago), Gpower only sold kits when you had them installed at their works in germany. (or perhaps outside europe at one of their partners). That was for a m54 sk1 system (so for an z4 3.0i), but the hardware is basically the same. Only their small sets (no heat exchangers, no larger injectors; not available for a z4m) were sold to private customers to install for themselves.
That's why/when I chose ESS (apart form hardware specs etc), as I wanted to do it myself.

But ironz4m has his kit lying on his diningtable (around the same time), so there are some inconsistencies in that matter and you might want to check up on that.