You have to do the big 3 upgrade,
http://www.the12volt.com/insta...~PN~1
It says after upgrading alternator, but I know people who just upgrade their grounds to 1/0 gauge and don't have dimming problems with stock alt.
I don't think Caps work at all. I've hurd mixed reviews about them, I have one in my lexus and my lights still dim. fyi
hope that helps.