This is a little unit that came from New Zealand that claims to improve diesel fuel combustion about 5%, delivering about 5% more power, and reduction in smoke.  I'm not sure if it worked but there seemed to be a slight poer increase.  Here is a pict of the unit.  You can find them on the web....

Here you can see it wired into the system at the bottom of the page.  It went in after the factory fuel filter and before the injection pump...  Email with questions...
andre@collegeinternetsolutions.com