Have you adjusted the lumbar toward the bottom which may affect how far out your lower back starts? I basically don't use the lumbar to support at all. That's the only remaining thing I can think of.

If this was meant as a response to what I mentioned earlier, I was talking about the seat bottom tilting, not the seat back.

__________________
'08 X5 3.0si - Alpine White / Saddle Brown interior
Specs: Sport Pkg, Premium Pkg, Tech Pkg, Comfort Access, Aero Kit, Style 433 staggered 20s on Conti DWS
Mods: Carbon 35 tint, LED angel eyes, GP Thunder 7500k fogs, H&R 20mm/25mm spacers, clear reflectors, gunsmoke-tinted taillights
Coded: Digital speedo, windows/sunroof/tailgate close via keyfob

X5 pics at Flickr