My truck has, for the last 5 years, been intermittently (but regularly, about 50% of the time) throwing a P0401. I have cleaned out the EGR tubes a half dozen times and replaced the valve & gasket with a new one 3 times. It won't go away.

The tubes are definitely clear. If I remove the valve while the engine is running and put my finger up to the holes, I have forceful blow from the exhaust system into the valve, and great suction going into the engine from the valve.

Is there something OTHER than the tube and/or valve which could cause the P0401 code to be thrown? Did I just get unlucky and have 3 bad EGR valves in a row (they are all different brands, Delphi, Standard Motors, Evan-Fischer)?

I'm at my wit's end, and my registration deadline is looming in a month, I need to put this problem to bed once and for all. Is there a way to reprogram the computer to ignore this and still pass smog...? I know the system is working, the code itself seems to be in error.