heres my attempt at explaining bumpsteer from what i have researched etc.
when the suspension is compressed or released, for example on bumpy roads when driving, the wheels will tend to toe out or in by a few mm. this gives the effect of the car wandering when driving over bumpy roads without your input(sort of like tramlining i guess)
From what i gather the whitelone bump steer kit, raises the angle of track control arm which reduces the bump steer effct giving you more control over the steering.
Feel free to correct me if im talking b0ll0x
Simple, cheap and potentially good mod