Thanks for all the astute replies gentlemen. I'll ask the alignment tech about cranking in a little more caster. The current setting is 1.5 degrees.
I've experienced varying degrees of tram-lining with wider tires on several cars in the past. The issue with my S4 is not severe but if it can be minimized I'd be happy.
I'll post results.
I’d note that Alfaholics adds even more caster than possible from stock with their geometry correction kit.