Having the preload set too high can make the shock top out more often. If your preload is set at the highest or second to highest setting, then back it down the the lowest or second to lowest setting, and the sound may stop.
I have been experiencing the "noise" for about the last month on Blue. Sounds like shocks are shot. Took them apart and to the dealer and they say they are fine. It started out as a once in awhile noise on one side at under 20 mph to every bump you find and both sides. Have tried the adjustments from soft to stiff, no changes. Thought it was loose bolts on the S3 lift, but all is tight. The axles have some play at the case, but don't know. Went back to the dealer on Thursday and told him it had to be the shocks and they said they would get some new ones. Now the waiting game for the shocks.
RockinRonnie: yes there are rubber bump stops on the Blues.