performance tuning chip-anyone tried??

[martint]

Just been on ebay & noticed some tuning chips from chipmydieseldotcom-about £250.
I dont want anyone telling me "would never try one etc etc",blah blah,but only wanna know if anyone has tried one of the more expensive ones £200-£300 etc
Do they give better consumption? More torque?

[benczuk]

I have a cheapish diesel express box http://www.dieselexpress.co.uk/ on my 2.2HDI. definitely improves throttle response, much more torque and arguably better fuel economy and fun.

no idea if it is harming my engine, but hopefully my limited yearly mileage means ill never know.