I spent some time with the front driver tire off trying to figure out where the rattle was coming from. I couldn't find anything there so I put everything back and popped the hood to look at the bolts on the chassis.
I finally found the culprit. It was the middle bolt nut, it was loose. I tightened it and had to give it several turns. Took the car out for a quick spin and the rattle is gone.
Now, when I had my springs installed, jsalicru marked all bolts in my suspension, and now the marks on this nut and bolt no longer align.
What does this nut do? Should I be careful about how much torque I apply to it? Do I need to look at other alignment things? I don't know what this part of the suspension is called :P Is this the top hat bolt?