As I mentioned in the other thread, and I thought might be the case, the box just plugs into the fuel temp sensor on the fuel rail. On a modern diesel engine, the accelerator pedal just sends a signal to the ECU to inject more fuel, and the ECU decides how much fuel to add and when to add it based on the inputs from various sensors, such as the fuel temp sensor, throttle pedal, engine rpm etc. To make more power, all you ave to do is add more fuel to the engine, but if you add too much, you get big black clouds of soot out the exhaust...
The way the tuning box works is that it replaces the signal from the fuel temp sensor with a value, which is fixed by the jumper links on the box. In simple terms, the fuel temp sensor is a thermistor, so it's resistance changes with heat. If fuel is hotter, it's less dense, so the ECU adds more of it, and the engine runs richer. If we unplug the sensor, and just put a fixed resistance in it's place, so the ECU thinks the fuel is at say 80 degrees, it will add more fuel, and the car will make more power. This is how the tuning boxes on pretty much all common rail diesel engines work, it's very simple, and does 'work' of sorts. You will gain power and torque, but there is no 'mapping', you're simply sending a fixed fuel temperature to the ECU, or possibly altering the original signal on a percentage basis. This means the engine might run richer at some revs and leaner at others, and will always run richer on light thottle positions than it would without the box fitted, so it will hurt economy, although that depends more than anything on driving style.
When I get some time, I'll have a look at the sensor on the CIvic, and see if I can dig out some specs on it, it may be I can do a DIY guide on how to make your own box, as it's pretty simple. Personally, I feel that a proper remap is streets ahead of this as a tuning option, however nobody seems to do a plug in remap via the diagnostic port, although it must be possible, as Honda can seemingly do it during a service.