I dont think a nismo power brace or bushings are a problem since i have both and i dont feel the difference when im driving in a straight line. It can be a lower control arm though, and if it aint then its your ball joint on your lower control arm. If the ball joint is loose it jerks to the sides really violently and if you been driving around like that its probably stripped (it happen to me when i took my suspension apart to put my nismo power brace
but i've changed suspension parts so much i can take out my whole suspension in 4 min).
If its none of this or if you are sure its not wheel/tire or anything thats loose related then what have you hit/changed that could of damaged the suspension?