Misfire after warm up does sound suspiciously like coil packs. The resistivity of the insulation decreases with temperature allowing a short to occur.The voltage required to bridge the gap depends on cylinder pressures, so at low throttle positions or higher engine speed when the spark is very advanced it will often discharge normally, but short when the spark timing is retarded.

IIRC, Ford had a penchant for very large spark plug gaps around 2000-around 1.3-1.4mm. This caused a lot of premature coil pack failures. I'd tap the gaps down to 0.9-1.0mm and see if that ameliorates the problem before splashing out on replacements.

I've had a fast idle but-only-when-moving problem before. I don't understand why it only occured when moving. I cleaned the ICV and recentered the throttle butterfly valve and it sorted mine!