@OP - I will suggest not to do anything for first 5k KMs.
No doubt Mehran brakes are quite hard - specially the newer cars - but it seems that there is some other minor issue as well. Which will hopefully fix in first checkup.
U can install Servo box and its an easy job but a monkey can ruin your car.
Also never buy used servo box as it never works - moreover it may leaks and can damage the paint of your car. It can also leak if not installed properly.
Just buy a new small size servo box and visit a good workshop - they will install it without any alteration.