An IAC would not cause a misfire. I would check the plugs/wires, especially the wires. There is no ignition module on the car so don't go and try replacing that. It's likely to be either the plugs, wires, or the coil. Start at the cheapest and work your way up. You can check the condition of the plugs and spray water on the wires in a dark place or at night to see if the wires are still good.
same problem with mines..i fixed it with plugs and wires, so either or could have been the problem...
you might also want to run some injector cleaner, make sure your getting enough fuel when hot.
00 GT transmission,Jmod,30,000 gvw transmission cooler
Air silencer removed(cone filter added w/ heatshield)
shaved emblems, doors, trunk, and antenna
chrome 95sc rims
20% tint all the way around,
6gallon air tank capacity, Viair 400c commpressor
175psi pressure switch
custom guages by Scott H. http://www.cardomain.com/ride/2733945