Here's a link to the Tunit item I used:-
As you can see, it is adjusted via a dial and can be re-programmed by the manufacturer. Probably do it yourself as well if you know what you are doing.
I used it on my 406 then swapped it over to the current vehicle. To do this I had to buy a new wiring harness as the plugs are different betwee the Bosch & Siemens systems that I had. I then sent it back to Tunit to be tweaked because it didn't work as well - it did when it came back!
Using the adjuster you can gradually increase the power. Initially, this can give better economy as you gain more torque, however, go too far and the gains back off as you come to the upper reaches. Of course, all of this, like everyday driving, depends on your right foot !
If you are considering a remap then I suggest you speak to a couple of places that offer the service. Tell them what you are after in terms of performance or economy and see what they tell you. Take your time and do your research.
Here's links to a couple of places that I have heard nothing but good about, may be some use:-
The last one, Tor Garage, is the one that I used. I'm not saying that these are the be all and end all, there are others who may be as good, if not better. This is just a place to start your research