Who is telling you that it is the master cylinder or the brake booster???? That is some bunk info. You should look at either tie rod ends, or worst case is the rack and pinion.
1. Does it drive straight? if not, it's tie rods. Either way, reach under there and see if you can twist the tie rod by hand. If it drives straightf yes then...
2. Does it make a clicking noise when you turn slowly to either side? if it does, it's a CV shaft. If now...
3. See how much the wheels turn when you slightly turn the steering wheel. If there is a space between the left and right movement before the wheels actually turn, it's the rack & pinion.
My bet is tie rods. Have you hit a curb or large pothole lately?
