I have replaced my factory front disc brakes with Baer SS4's, at the same time, I replaced the brake booster/master cylinder & proportioning valve. In addition, pulled all old brake lines and replaced them with "Right Stuff" pre bent brake lines to fit.
I fully expected this to be a really nice upgrade, however, my new Baer fronts are weak and when fully applying brakes ( hard stop ) the rears will lock up.