Brake pedal fade

[VDOG]

Ok I have read some of the previous post on brake pedal fading.
And I would agree that the master cylinder is the problem. But I had a new master installed about 4 years ago and still had pedal fade so it was found that I needed wheel cylinders. My truck might have 1000 miles on it since the master install. Change the wheel cyl's and added front disc brakes.
Now I know I need a booster for real stopping power but until then I should not still have the same problem of pedal fade. help!!