I kept delaying and delaying my AAL installation because of constant travel for work... well I finally got fed up and stopped by my neighborhood garage and had them installed on my 06 DC 4x4.
I wish I had a before and after picture. Those leafs were as flat as flat can be and now they've got the most beautiful arch... took the lift blocks out and now it rides 10 times better. I didn't realize how crappy my ride was until now - ugh.
All the talk about doing an AAL is true - got get it done!
My stealership wouldn't do the TSB on mine because I installed lift blocks to override the sagging problem!!!