Dirty fuel filter

Last night we noticed the fuel filter on the VeggiGen was getting plugged. How do we know? RPM surging, and little to no fuel from the return line. Our filter is in a vacuum position. The pump sucks. This afternoon, I replumbed the filter into a pressure scenario. Now the pump blows, and I'll be able to get more life from the filter. No more surging or rpm variation, and a full steady return. I still need to replace the filter ($12), but not as often. The pump is protected by a prefilter in the fuel drum as outlined in our sock filter post.