Brake pedal still soft after new mc new booster new ext vac pump new disk system in rear all new lines and blead system 4 times and still the same

who did the brake bleed ? and how was it done ? proper bleed requires 2 people. one person loosens the bleeder the second pumps the brake. once the bubbles are gone the person holds the petal close to the floor and lets the person tighten the bleeder. person then pumps the peddle till it is hard and you move to the next one. always start from the one closest to the master and move to the next furthermost. so driver side first then passenger then both the rear brakes usually driver side then passenger side again. if your brake peddle is still loose after that you most likely have a master cylinder issue or a hidden leak.

Yes, the problem is still due to air in the system. Deathjam has the proper sequence. Using a jar is the old way of doing it. Today there are several kinds of auto and semi_auto bleeders. Harbor Freight has several and some are very inexpensive.