Here is the page with some more specs on this:
http://www.gruppem.co.jp/en/home.html
9.1 kg is pretty damn light. It does sound good, too, but I wish there were some drive-by videos. The only video available is stationary.
I am not sure about what to make of those performance numbers. The deltas seem optimistic to me...
For stock GrouppM claims stock does 16.57s, but BMW's number is 15.8s.
GuppeM claims 15.33s for the intake PLUS the exhaust.
Regardless, I will seriously consider this.