Careful with those fuelling gadgets - they only fool the ecu a little and results are inconsistent.
LOTS of people who have had them found they have caused damage somewhere in the engine as it doesnt seem to do the job properly - not sure what goes wrong as it is not always the same fault car to car. A proper remap seems to be the ONLY way to go.
I havent used these myself - Ive always scraped together enough cash for a remap.
Ive used diesel driver
http://www.dervhead.com/xmb/index.php as a sensible source of info for diesels. There is nothing on nitrous over there but its a good source of general diesel info.