A fuel polishing rig is maybe $100-$150 if you buy the parts and make it yourself. I did that when I discovered that I had diesel bug just before we were to set off on an offshore passage to the San Juan Islands. I ordered the parts, built the rig, and did 5 or 6 turns of the fuel that was in the tank through the filter with multiple shock treatment level administrations of BioBor JF. The result was that we had no issues crossing the Columbia Bar, going to the San Juans, and coming back to cross the Bar again.
