I'm sorry to hear that you are having lower back pain due to the sports seat. Have you tried sitting in the multi contour seat? I have 35d on its way to me and I probably should have ordered the multi contour seat option ($1200). I have an E93 335i with sports seats and it didn't bother me, so I passed up the option. You should go back to the dealership and just sit in one and adjust it to your comfort level to see if your back pain goes away.

-DaRip

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2010 E70 35d /Vermillion/Tobacco w Dark Bamboo/Sport/Premium/Cold/Tech
Completed on 2/2/10, in my garage 2/24/10...

My 35D Mods: http://www.xoutpost.com/bmw-sav-foru...d-weekend.html
07 E93 335i Cabrio /Platnium Bronz/Cream Beige w/ Dark Burl/Sport/Premium/Cold/Nav/CA/Ipod USB/PDC
Arrived to Port Hueneme 5/15/07