Need help with Braking problem

[71Subman]

Hey guys, I am at a loss to figure out why my brakes don't work like (I think) they should. I have new rotors/pads and Drums/shoes all the way around. new master and wheel cylinders. I have bled the lines to the point I can do it in my sleep. My booster seems to be working OK and I have replaced the rubber lines with braided steel (when I did the lift). The brakes feel fine, pedal-wise, and work fine under 'normal' braking, but I can not by any stretch of the imagination or slamming of my leg(s) get my suburban to stop fast (in a panic stop situation), let alone lock the tires up (unless I'm driving on ice. Am I expecting too much? I have to leave LOTS of room in front of me in traffic, to make sure I have time to stop. It feels like an overzealous ABS, but I couldn't find that on the options list for my 71 Sub. I have even resorted to taking it to 'experts' and have been told that my brakes just need to 'break in'. Well, there's about 3,000 mile on them now and no change. Any ideas??