Excursion ABS Problem?

[skidmann]

I have a 2000 Excursion with a 7.3 PSD 4x4. It keeps warping the front rotors. It is on it's 4th set!. I have replaced almost everything in the front end. New: rotors (x8), brake lines, calipers, and hubs. Also just recently redid the rear brakes. The problem is definately the front. It pulls to one side or the other constantly. It is not a strong pull, but during a panic stop it pulls to the left mostly. During a gradual stop it pulls to the right as I slow down below 20 mph. Sometimes it stops straight and true. I have no abs light on and it throws no codes. A few people have speculated that it is the abs unit. I called the dealer and they said there is a electronic unit ($800) and a hydralic unit ($900). It could be either or none. They only sell separate of course. Any ideas?