Sway/Drift fix?

I'm a good ways from finishing the suspension on my car but I'm anxious to fix the one problem I'm dealing with since the addition of the wheels and tires. I've noticed while driving the car likes to drift or sway from one side of the road to the other at the higher speeds. Is it the additional weight of the wheels causing me to notice this? What would a good fix be for it? Aftermarket swaybar maybe? Also I know of maximum motorsports subframe connectors being top quality should I go with full length on those and have them welded in or bolted? And I need some opinions for the strut tower brace bar are they worth the money or do much at all?

Yea my initial thought was that but when I had the shocks/struts and springs done I went and had it aligned. I never did do the caster camber plate upgrade after the spring installation so maybe that has somethin to do with it also.