When you have it apart, pull the boot off the coil pack and inspect the end for cracks. This was the same symptom I had when I had a coil with cracked plastic end. Under load or higher engine temps the crack will spread allowing for a loss in spark and a misfire. When you let is sit there and idle it would not throw the code. However, as soon as you put a load on it, pop there comes the code.

Logansportage <img src="/forums/images/graemlins/patriot.gif" alt="" />

White 1998 4 door KIA Sportage 4x4 w/Eibach 2.5 spring lift and TJ rear coils, 4crawler 1.5 body lift, Monroe Sensa.trac shocks, Bosch 4+ plugs, Eaton LSD, 31x10.5x15 BFG KM tires, 2.5 cat back exhaust w/SpinTech muffler