stiffaning capacitor?
 

ig ot big three under my hood 1 gauage power ground all the way back do i need one ?

Yes, buy mine.

The ground shouldn't go all the way from the battery to the amp. It should be on a clean metal spot on the body, no more than a few feet from the amp.

If you do that and your lights are still dimming, get a cap. Unless you can get a high output alternator for less (or reasonably more) :)