Better but still hard to stop

[lakesidedc]

Greetings from NE Michigan. Been using this site some lately...thought I should join. I am currently working on a 1988 GMC K1500 4x4. Got it as a Florida truck, but turns out, not. I have replaced the front pads, rotors were fine. I have replaced the booster, helped some but still not like my Ford van when it comes to stopping. I need to push hard to get it to stop like I want. I lifted the rear wheels off the floor and put it in gear. Right wheel drives and takes some pressure to get it to stop, then the left wheel starts turning and stops quick, then it will not turn without acceleration. I understand it has RWal system. I am suspicious of this system. Any Ideas? I am known round here as dc. thanks. ps is a 700r4 trans