The same thing happened to me this past spring after I had done some suspension work and changed front pads, too. The car pulled disturbingly to one side during moderate to hard braking.
I bled the brakes, but no change. On a whim, I guessed maybe I had contaminated one of the rotors/pads with a smidge of grease, however no contamination was visible. I cleaned all front brake components with Brake Kleen, and went out for a drive. My problem was gone!!
I hope you are as fortunate.
David