Here are some links to sites which can supply a display system for Diesels, which could help in the setting of the fuel system helping to eliminate the black stuff.
http://www.techedge.com.au/vehicle/wbo2/wblambda.htm
http://www.motec.com.au/plm.htm
This one is a goodone explaining the methods
http://www.innovatemotorsports.com/supp ... al_3.0.pdf