96 yukon breaks low on pedal

Hi every 1. I was hoping for some input. my 96 youkon has breaks but it takes half the pedal befor they start to work. I have replacesd the master cylinder (no help) I have adjusted the back drums (no help) new front pads and roters. I am kinda loosing my patients with it. They have bin like this since I bought it a year ago. I thought it was normal but then I drove my frends 1500 and they wrer at the top. does anyone have any input. thanks

Look at the last post in this thread by maxwedge: http://www.automotiveforums.com/vbulletin/showthread.php?t=630692

If the combo valve is stuck then you will not get a good pedal.

//2000CAYukon