Sparkplug wire resistance should be VERY close to 1000 ohms/ft. At 1500 ohms/ft they need to be replaced. Most often they will either be good or junk.
The issue you describe *could* be EGR related, but you should get a code for that. I do agree that if it is bucking/missing plugs and wires would be my first suspects, but do not overlook a dirty MAF sensor. You can inspect and clean it by following the directions here:
www.crownvic.net/cleanmaf.html
Now, if you do think that the engine is misfiring you need to disprove the torque converter as the cause. When the TC "shudders" it feels EXACLTY like going over "rumble strips", that is like a fast vibration. A true engine misfire is MUCH slower and no anywhere as consistant and softer. In a way like being tugged by a slackened rope... tug, tug.