Idle Air Control is first on my list (happened on my 98 4.0 and is a bolt on fix) $20 on Ebay

Intake Manifold Gasket (there are 2 one on the top and one on the bottom) bottom usually goes first. Try using a squirt bottle filled with water and as it is idling and stumbling spray a stream (not a mist) at the edge of the gasket. If it stops stumbling that is your problem. R&R is easy just be careful to torque the bolts evenly .

Coil pack wire leads arcing. When it is dark, open the hood and let it idle and look for the glow when the wire insulation break arcs to the block.