Now I actually have a 2010, but I haven't been able to get an answer for my question, so maybe you guys may know. Dunno if this is supposed to be normal, but when I adjust the lumbar lever all the way to the forward setting. The lumbar support is just barely a little past completely flat. Now when I pull the lumbar lever all the way back, the lumbar support concaves inwards pretty far where it almost feels like the seat is a turtle shell lol. In other cars I've sat in (not other G37's) the lumbar support adjustment will actually arch your back significantly and force you to have a very straightened posture.

 

Mine isn't all that great on my 08 either.

 

Mine seems great, I used to have some probs with my previous car, but this one seems nice...

 

my 07 pushes out quite a bit, i can never push it all the way out while driving cause it gets uncomfortable with that much arch for me.