What's the most likely cause for a PO402 code? on 2000 Ford Explorer

Truck runs and shifts fine when cold, as motor warms it lacks power, surges, and has shift problems but idle is okay.

1 answer
SOMETHING IN THE EGR SYSTEM IS MALFUNCTIONING OR POSS DPFE VALVE. SEEK PROPER DIAG AND EST AS THERE IS SEVERAL THINGS IT COULD BE, INCLUDING PLUGGED EXHAUST SYSTEM