2004 Kia Optima lack of power

Check fluid level in transmission and scan for codes.

Fluids are fine and there aren't any codes

Here is what I've done
Spark plugs and wires
Tps sensor
Ignition misfire sensor
Mass airflow sensor
Crankshaft sensor
New coil packs

I myself owned an 03 optima and ran into the same problem and had to replace the transmission. I would take it to a tranny shop and see if they can verify. The clutch packs may be worn out inside or some other internal defect.