Where ya from fella? I was going to immediately suggest contacting Van Aaken as they are the daddys at diesel tuning, but see you've got their name in your siggy pic?

IF you ARE from near van aaken you should be at our monthly Berkshire PF meet

As for tuning, a better turbo [new hybrid], a better intercooler and a DECENT remap should cost the best part of £800-£1000, but for what benefit? In my opinion you'd be getting to the point where the fuel consumption isn't far off a mildly tuned petrol engine, defeating the purpose of having a diesel anyway [unless you tow?] so why not get yourself an RST as a toy - which you can pick up for the same price

P.S you can't run a diesel on Nos, cooking oil maybe