Hmmm...no action in the IDI forum. Lets slide this one down to the BioD forums and see if we can get you an answer.
I've been using Biodiesel in 9 different diesels with IDI and without for over 2 years now and not one fuel related problem yet. Just remember to change out any natural rubber fuel lines and change your fuel filter early after changing to B-20 or higher.
I've got a 1992 idi which I have run many tanks of bio diesel in the last 14 months. just change your fuel filter soon after switching. as for the natural rubber lines, they should be ok as long as there is no considerable seepage so that the stuff gets on the out side and eats away at it. I use either B 50 or less made out of waste vegetable oil. If you can get stuff made out of soy oil, that would make it burn better. if your idi is not turbo'd, it will not burn the bio diesel as good cuz it takes more oxygen and boost to burn that stuff.
BD is more environmentally friendly than Petro for several reasons. Even B2 shows reduction in CO and CO2. Pure BD is CO2 neutral in that all of the CO2 released was initially removed from the atmosphere by the plants that produced the oil seed crop.
Additionally BD is biodegradeable at about 3X the rate of Petro so spills are less problematic