Have a squint on ebay, sometimes those ECU boxes come up for about 100-150 quid. That's ususally the cheapest way to get extra power. You could always try upping the boost pressure on the turbo but I think it's not straightforward trying to work out how to do it... Someone from Oz did it and posted it on here if you look for it.
i have a diesel power box, it plugs in the sensor in the end of the fuel rail, and gives it a false reading,
cant tell much difference in 1st and 2nd gear but the tourq if defo improved in 3, 4 and 5th especially on uphill motorway's etc mine was about 200.00 off of ebay, think they are a bit less now,
or il sell mine for £50.00
I was told to make a new gasket, thin metal, and block the exhaust gas return, situated on the right side of the engine as you look at it, this definetly helped and dosen't do any harm I'm told?