I have run the gambit of front brakes.
I think I have had every possible problem.
More often than not when my brakes start to pull it's due to the caliper pins getting gummed up.
After 280,000 miles of driving in Southern California stop and stop traffic, I have found that it's very important to lube the caliper pins and the areas where the caliper slides on the spindles
every 1000 miles.
You seem to have a "warm" brake pull.
It's pretty easy to check your front brakes and real quick too.
Just jack up one front wheel at a time and give them a good spin.
Here's a link to a video showing the proper amount of spin.
http://www.youtube.com/watch?v=RGHd5-j2TQk
If your tires rotate freely you should check the rears for oil contamination and also check the wheel cylinders as they can also stick and cause your truck to pull to one side.
Also check out my readers gallery here on the YDR for more great tips and tricks.
SFB