Actually, we are both correct. However, the spring rate goes by size. If XII is using a 14" linear spring, then they are limited to a 350 ppi. With the 12" they are limited to a 600 ppi. Eibach has up to 650 ppi for a 2.5" x 14" linear spring.
I should have been more clear in my previous post, as I was already assuming that they are using the 14" length spring, when in fact I actually don't knkw the length they are using at all.