Been having this trouble too. My Contour had its plugs changed for the first time at 200,000 km. It was actually running quite well until then. Now, I get the exact same symptoms "rgthoma" describes.
The plugs and fuel filter were changed... but not the wires. Since then, I have changed the wires (Motorcraft 9mm).
Last weekend I cleaned the EGR passages after removing the throttle plate. They weren't so bad. I also just added some injector cleaner.
What seems to be happening is the engine senses unburned gas and goes to full lean. Then it loses a lot of power and has trouble going up hills. (Especially with the a/c on). I don't get any CEL light, flashing or solid. Just a stumbling when going up hills in fourth at city speeds.
But, since cleaning the EGR passages and adding the injector cleaner, it does seem to be running better. At least the problem happens less often.. and when the car is running well, it runs very well.
We'll see after the full tank of gas is run through.
- Randall
