[MotleyCruze]

I really can't see the point of tuning the diesel as a road car? It would be cheaper to buy an older car with a big engine and tune that and get some real performance.

Both my former TDI's were chipped, and it's a world of difference. It was astonishing how much better they were, and if you can keep your foot off the fun pedal, the economy's about the same.

 

[MotleyCruze]

In the "old days" they would physically remove the ECU (engine control unit) and either reprogram it or replace it. Hence the term "chip". Nowadays they can access the software (mmm, firmware I suppose) in the ECU via the OBD port. My understanding is that they download the program (the stock tune), revise it (the tuned, tune), and then upload the program back into your ECU, again via the OBD port. I had two Jetta TDI's that were "chipped" (i.e. tuned) and they were terrific.