Originally Posted by YerBuddy

The different letters denote the different spring rates and how low of a drop you get. For instance, the estimated drop for the K spring is 1.5" front and 1.5" rear. The P springs are less of a drop at 1" front and 1" rear. It all depends on how low you want to go.

AM sells Eibach and that's also a good choice. If it were my decision, and I had to order from AM, then I'd probably choose either the Eibach pro or FRPP P springs. Both are a nice way to take the 4x4 look out of these cars without giveing up much ride comfort. It won't be as "bouncy smooth" as stock; rather, more planted and looks a heck of a lot better IMO; more level. I went with Steeda Sports and don't regret it whatsoever. Mild drop is what I wanted...and exactly what I got (approximately 1" front & 1.25" rear).

However, it's also addicting...beware!

The only other thing you would need is an adjustable panhard bar to bring the rear back to center. Easy to install and easy to adjust. If you are not going to do all the work yourself then have whomever you are paying put it on at the same time. I went with a BMR adjustable PHB, but only because I had a coupon too. Saved me some cash which is always a good thing.