I just finished installing BellTech coilovers (BellTech part number 21017) on my 9-7X. BellTech is owned by KW (a German suspension company) and this kit actually uses KW Variant 3 shocks (adjustable compression, rebound, and height) with KW springs. It included front coilovers (springs and shocks) and rear shocks/springs. The rear shocks were designed to replace the stock shocks in the rear. I left in the stock airbags. The kit came with springs for the rear, but I didn't use them. It seems that either way is acceptable. The installation was fairly easy (there are how-to guides on tbssowners.com) and only took about 4 hours.
http://www.kw-suspension.com/en/30_Products/20_KW_Coilovers/30_Variant_3/index.php









Tim
http://www.kw-suspension.com/en/30_Products/20_KW_Coilovers/30_Variant_3/index.php









Tim