Start out by running Startron Tank cleaner for a few tanks. If it has time to sit and work for those two tanks it would be better. (In other words, don't use it in two tanks on a long one day trip and expect the tank to be clean.
)
It is available from
www.westmarine.com among other places.
Search on this forum for Startron and tank and see what you find. I love the stuff.
After that watch your injector return lines. The MB rubber does not seem to do well with biodiesel. Maybe their new lines handle it, maybe they don't. I sell viton lines the absolutely do handle biodiesel and they are cheaper then the overpriced MB lines, IMHO.
I also sell o-rings for the rest of the fuel system. I figure them out as people ask. If your engine is not one that I have figured out, let me know and I can work on finding the right ones for your system.
The larger fuel lines (5/16 and 3/8 inch) can be replaced with standard auto zone fuel line. It seems to do very well with biodiesel.
-Jim
(PS Buy from Fastlane when you can. Support the site. I only sell what I have needed and they did not offer.)