Car will throw fault code p0401 only after fueling but not everytime. on 1996 Lexus SC300

Changed egr valve vac Modulator and ox senors. I even changed gas cap.

Asked by for the 1996 Lexus SC300
THESE CAN BE VERY TRICKY, DID YOU CK PORTS TO SEE IF THEY ARE PLUGGED WHEN EGR WAS OFF. YOU MAY ALSO HAVE A SENSOR ISSUE