[mr0077]

Chad, one other suggestion I didn't read above (though it was built into Bob Putnam's advise)...check your suspension bushings and tie rod ends. If you have a bad bushing or tie rod end, it will allow one wheel to toe out under braking, causing it to pull to that side. Sounds like you've already checked all the brake stuff...
Lotsa Luck, and let us know what you find.