One of the few things I have NOT liked on my 2014 i3 Rex is the lack of lower back support on the seats. My passenger seat isn't quite as bad, so I suspect it's partly just normal wear and tear on a five-year-old car. Still, I wish BMW had given us at least a rudimentary manual lumbar support adjustment! I came up with my own by putting just a little extra padding in the seat cushion. This website: https://www.jesseweb.com/tech/repairing-the-bmw-i3-backrest-fabric/ tells how to remove the back of the seat on the i3 to gain access to the springs and backrest cushion. It's not difficult, and where he talks about the difficulty in getting it loose from the top, I just left it hanging. With the bottom and sides popped loose, it gave me enough access to the lower back region of the seat. All I did was buy a square of 2" thick foam from Hobby Lobby and cut about a 4" square of it. I worked that between the springs and backrest cushion to add a little extra padding to the lumbar region. With a little trial and error, I got it to the point where it feels pretty good on my sensitive back!