Brake pedal is stiff and the car pulls left or right when braking (occasionally)?

Dear Ken,

Thank you for your reply.

I took the car to a Nissan specialist garage center, and they examined every brake hose, and every abs sensor and they also said that the problem is the ABS CONTROL UNIT. They ran a diagnostic control, and they told me that there is an error code for the abs control unit. And I then asked "Okay, but then why does the brake pedal become stiff? Doesn't that mean that the brake master(servo) is malfunctioning and not releasing the pressure correctly? Doesn't that mean that I also have a malfunctioning break master? " And their reply was "because the abs control unit is not working properly and does not send the correct signal to each wheel it is causing the brake master(servo) to not function properly".
They said that my pathfinder will be ready tomorrow and asked my permission to take the car for a "long" test drive to make emergency brake stops in both tarmac and gravel to rest assure that the problem is solved. Fingers crossed my torture will end tomorrow!
No I did not change the brake hoses because TJM on their lift kit manual said that there is no need to change the brake hoses (to extended brake hoses) for my car because even on the position of most suspension travel the brake hoses are not extended beyond the manufacturer limit. But yet again, I have the suspension already for 2 years and I have had this problem the last month.

No ABS lights, no light came up on the dashboard ever, no check engine, no ESP light, nothing!
I got the car today, the head mechanic of the shop said that they installed a used abs control unit(coming from a 2009 Navara d40, which most people think that it is the same abs control unit, but along my ownership of the pathfinder I found out that a lot of parts on my car are different from the Navara d40 because my car weighs 2,460kgs and the Navara's weigh approximately 1700kgs, that is what I have been told) to see if it would give error lights on the dashboard through the pathfinder's ecu, which it did come up with ABS-ESP lights and check engine errors, then they reset the system through diagnostics and had a abs control unit shipped from 150km away that was specifically made for my car(it was from a used 2010 Nissan pathfinder r51, I could not wait 1month for the new part and pay 3500euros for it). They installed the abs control unit, did all the necessary diagnostic system setups, then they did a long test drive in both gravel and tarmac(i was constantly checking the live location of the car through the GPS unit I have installed in my pathfinder) and then they called me that the car is ready.(They regreased all the calipers, checked anything related with the brake system, and changed the brake fluid before installing a new abs control unit just to make sure that everything was working in perfect condition), I picked up the car today at lunch time, the brake pedal immediately felt like normal as soon as I put my foot on it, it is smooth and then gets stiffer as you press the brake more and more, I did heavy braking in every single pothole I have found while releasing my hands of the steering wheel and my pathfinder is dead straight! Not even a millimeter to the right or left while breaking, ABS system works flawlessly and it even feels that it stops much faster!
Super happy with the service and that I have got my mini bus(my pathfinder :-D ) back and all the problems seam to be solved.
Apparently, it was not the brake master that had issues, and indeed the problem was coming from the malfunctioning ABS unit causing the brake master to malfunction as well.