sochonr

I have a 1996 Subaru Outback with 2.5 liter engine. Every week get check engine light with code 400, insufficient EGR flow. So far have replaced EGR valve, replaced backflow pressure transducer, and cleaned EGR passages. Could pressure sensor or pressure switching solenoid be defective? Is there a test for them? The EGR valve appears to operate normally with proper stem movement. If the pressure sensor is bad wouldn't other codes to set or the code appear more than once a week? Any ideas? Thanks.