honestly I am confused now.

I have a 4.4 2002 model, which does not have "self leveling air suspension", as there are no buttons to change the ride height, but only a "air suspension" in the rear...correct so far?

The H&R springs cost only about 2xx USD for "air suspension" X5.

This kit here costs 4xx USD.

Can I simply get the the H&R spings alone? Or why would I need this kit?