Bump steering is the vehicle will steer one way or another when the front tire encouters a bump. If the tie rod joint at the centerlink is not in the same plane as the upper and lower control arm bushings the tie rod will swing in a different arc than the spindle, As the spindle goes up and down the tie rod will effectively push or pull the steering arm in or out.
I wouldn't cut a coil as lowered springs are available but if you do do not use heat to do so. Use a cut off wheel.
Hope that helps.