My motor has a miss in it when under a load...

In many circumstances like this I would typically suspect the secondary ignition components: such as ignition wires leaking voltage causing a cylinder miss. Under load designates a drop in ignition signals. You may have a defective component ex: a cracked plug.....if the ignition is good I'd check for a lean or restricted injector.

kia spectra 2002 engine runs good out of gear skips went in gear