My 2000 had the same problems. As mentioned by "snicklas" the calipers are most likely sticking. My truck would sit for a month or two on occasions during the winter outside. I've gone through 3 sets of caliper in 155,000 miles.
I was told several years ago to use only the Motorcraft oil filter by a mechanic that worked on 7.3's in International school buses. As I recall, he explained it had something to do with oil pressure and HPOP to the injectors. Has anyone else heard of this?