Most turning tendency is not alignment (tires or bushings) but yours may actually be alignment related, let me explain my experience with it... Caster is the alignment setting to adjust LH or RH pull, but it's very subtle... and there's not to easily change with regard to differential caster (usually off slightly as roads are crowned)... unless you're mistaking steering wheel not centered as turning.
However, slightly LESS toe in for the front can be helpful in my experience with the ST... when I first got the 2018 car in July, I just drove it. Then for autocross prep, got out the Longacre toe plates, grease plates, camber tools, checked the alignment, I maxed out negative camber, and set toe-in at zero. I had a little too much toe in prior to start about the same as you... and the same with two other local ST's that I reset the toe on and huge improvement.
Result was brilliant, I could take my hands off the steering wheel on the highway and it tracked very straight and more stable than ever. Also the tire dust from the front fenders was no longer an issue.
The logic is it's a light weight car, with more weight on the LH side the car favors a tendency to pull to the right if you're on the high side of the standard spec.
Since then, with two different ST's and many different suspension configurations trying different stuff, that's what I've learned... you'll have all the "experts" and "alignment shop idiots" arguing so I don't really care, but hope that helps.
