I own a 99 e150 and have had the same problems. The rotors will rewarp the first time ya hit rain no matter how long or short since you replaced all the brake parts. problem is that 90% of the braking is on front wheels and rotors are just simply on fire and will warp very easily. I fixed by installing 3/4 ton rear wheel cylinders (same footprint) which increased rear brake effectiveness by about 40%. the 3/4 ton's are about 3/16 inch bigger than 1/2 ton. increase the surface area and you increase the force...now that rear brakes do something there isnt as much load on front brakes...i did research this thru ford dealers to get to the root of the problem.