I had a very similar problem with my contour way back when. Whenever you would gun the gas pedal, the car would take right off, but once you hit higher revs it would hesitate a little bit, made me think I had a weak fuel pump. Days went on, and I never fixed it because it never really was a problem as I rarely ever beat on my cars, Then came the summer... The true test for any car, 90 degrees and 70% humidity, I then figured out really what was happening, because the problem got way worse when it was hot and humid out. It was definately a misfire. I ended up having to replace my coil pack because it was defective (I had just replaced it less then 6 months before these problems). Also, my plugs werent helping the problem, you are only supposed to use Motorcraft/autolite plugs in pratically any ford engine, I used champions in my tour, BIG mistake, cracked the porcelin on one of the plugs, WOOO that was a fun experience.
. Thanks for posting your experience.