Had similar problem it was a bad/binding caliper. The symptom was on a hard stop the vehicle would pull to one side. Was not noticeable when stopping normally. The problem was the caliper on the side opposite of the direction of pull. Also the rotor on the bad side was noticeably cooler. I agree with the others, do not see how it could be power booster issue but I guess anything possible.
Guess you could swap front calipers,if possible and see if the problem moved to the other side. But that seems like overkill to diagnose the problem.
good luck....

1987 Raider/Silver/5speed/AC/Off road package
356K miles/owned since new/daily driver