I was under the impression that D3 has a fix for the squeaking on their lowering springs . They have a nylon sleeve that you wrap on the top of the front springs to eliminate the noise. If you haven't requested these sleeves contact D3 so they can ship them out. If anyone has installed the sleeve's and still has noise issues please chime in. I will contact them to make sure this issue is resolved. BTW i have no affiliation with D3.
I was surprised how well the stock rear springs were isolated from metal with a thick rubber donut at each end. I haven't started to work on the fronts yet, but are they as well isolated from metal too?