Hey all, I have an issue I hope some of you can shed some light on...

A friend of mine has a 96 Chevy K2500 Suburban with the 7.4 in it. Recently the brakes have peen presenting serious issues where the pedal is next to impossible to push and he has to almost stand on the pedal to get it to stop. He already replaced the hydro booster and that seemed to fix it but after a day or two the issue returned.

Can anyone suggest what to do next?