why not put 2 cat converters on there
just to pass
then straight pipe it after

 

You will have high NOx with the high cetane fuel over here all the time since it effectively advances timing. (Usual setup for 45 cetane, average pump diesel in Europe is around 55)
I'm using a good proportion of biodiesel (cooler burning stuff) like 70% for mine to pass NOx, soot does also go down. I would like to point out that I've replaced my fuel lines from the tank forward and mine is a 24V... don't know how a 12V would react to bio. (You will need more than 50% bio since bio has higher cetane than dino- around 60, but if using enough it will lower combustion temp and therefore NOx)

Cappy, if you like give me a holler

AlpineRAM

 

Thanks guys, good thinking. Sounds cheaper than a cat. Will try the fuel first. Not sure if we have bio diesel here though, darn... Really appreciate the help.