What the???

Hello! I just bought a 2001 Escort SE with 83,500 miles. I changed the tires and flushed the transmission. The car drives well. The problem arises when I am in Drive and at a standstill. The engine idles somewhat roughly and it seems that the rpms drop. It doesn't do this in neutral, park, or reverse (that I can tell). Plugs are used but not bad. It has not stalled and starts easily. Accelerates smoothly. Carfax was clean, spotty maintenance. Any thoughts?

Plug wires. IAC vlave. Coil pack. Air filter. Fuel filter. In that order.

yes i agree with jetlee