Maybe someone here can help this person out -

http://biodiesel.infopop.cc/eve/forums/a/tpc/f/159605551/m/6311015082

May want to ask the person to join here and post. Do the diagnostic checklist. I am not sure what kind of truck he has, may be a 6.2L. In which case, go to the 6.2 section.

By the way, there are a lot of instances here that the IP gives up because of Veggie. You can also point him to the Alternative Fuel section.
It tends to gel when temperature goes below 40F, it also retains a lot of water.

My suggestion is to get some extra IP and keep an IP rebuilder on the payroll and learn to replace IP. From what I heard, it is cheaper to run veggie and keep changing the IP since the amount of saving yearly is more than the cost of IP and replacement.