Did you even the caster out between the left and right sides of the car? Caster is set to about 4.5 degrees on the left side of the car and about 3.0 degrees on the right side of the car. Did you add more caster so you have the maximum allowed 6* right / 4.5* left? Or is it an even 4.5* on either side of the car?

Caster will make a huge difference in how the car tracks, pulls, and turns.