Go here and read this:
http://www.contour.org/mods/mods.php?s=howto&displayid=39Find very last photo. Take circular filter disc out and throw it away. Throw it as far as you can. It is too fine and too small and you don't need it because there is a standard sock filter inside the pump module anyway.
They all plug eventually and this will almost always solve the problem you have described on your returnless system.
While you have the pump out, make sure that there is no obvious fuel contamination (there probably won't be). It also helps to have a replacement "O" ring gasket since the old one often swells when removed and sometimes cannot be reused.
