Enigine trouble

Let me start by saying that I came online as a last resort. I own a 98 Contour, appx. 126,000 miles, Auto transmission. The vehicle upon start, will stutter, when the gas pedal is pressed the engine will sound and act like it is going to die. After warming up for 1-2 minutes the car will run. The second problem being, driving down the highway (60-65 mph) the car will suddenly lose power. Pressing on the accelarator will make car slow down more. Releasing the pedal will give the engine a sudden short burst of power ( the same can be said for when the car is started ). When the car is slowed to under 30 mph or has came to a complete stop the car will take off with little hesitation. Which leads me to point out that the car also has a slow start from a complete stop. Now I have replaced the oxygen sensor in the engine compartment (ford has told me that this is the only o2 sensor on the car but other mechanics have told me otherwise) also replaced the fuel filter. And checked the catalytic converter. None of these have fixed the vehicle. I'm stumped and it seems that so are all the mechanics in my area. I was told however that it may be my coil pack. But I am not certain. Any help would be appreciated. If you think you can help shoot an email to theryknow@hotmail. Com Thanks.