Bump steer is generally a geometry problem.
When the car is lowered beyond the limits of the standard parts, the geometry of the steering arms is compromised.
This can be cured with a variety of products.
Example: Ikeya Formula tie rod ends.

Use of these or similar products will allow you you achieve parallel steering arms & reduce if not negate bump steer on a lowered car.
Obviously the wheel alignment must be correct too, as this will only agrovate the situation.
When combined with roll centre adjusters, you can achive excellent handling when the car is set a a low ride height.
Without use of such products, it's difficult to get the most from your dampers at very low ride heights.
NB: At very low ride heights, other products such as adjustabletoe & camber arms are also advantageous to achieve desired wheel alignment.
Hope that helps
Cheers
Adrian
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