There are lots of tuning chips available for the Ford diesel engine. These range in price from abot 75 to 400+. Has anyone had experience with them?

Typical units available on Ebay can be bought from about 85.00. Many look to be the same, and most offer a power increase of up to about 25%.

Does anyone on this forum have experience of these devices, and if so, can they please advise which are the best?

Personally, I'm looking to increase the low speed torque spread on my 1.8TDCi engine, but any information welcome.