my bumpsteer got worse when i installed X2 ball joints lol. If your car is lowered you can still have bumpsteer even with stock height ball joints. I'd say it could help you if your pulling happens when your car rises and falls on it's suspension, if you're just hitting ruts in the road then a bumpsteer kit wont help.
Steeda recommends a bumpsteer kit for stangs with X2 ball joints.