then can you tell me please how your box works and what exactly you tune? And what data you gather while you do it to confirm the longetivity of the engine? The fact that you can mess about with Porsche doesn't make you an expert.
I don't repeat crap that i read on Ebay, i'm a professional engineer with experience in engine development both diesel and petrol.
Having looked carefully at the tuning box options and digesting as much technical information as I could it is clear there are two types in use (Note here I am excluding simpler devices that simply pass the common rail signal through a potential divider to fool the ECU):
1) The PSI box, tunit boxes etc. all intercept the common rail pressure transducer signal and feed a modified signal to the ECU. The exact value of the modified signal depends on a range of parameters and may include throttle position, engine revs etc. i.e. the pressure transducer signal is digitally remapped. Normally the modified signal suggests that the pressure in the common rail is lower than is actually present thus causing the rail pressure to be increased. I think the pressure is regulated via the pressure release valve and not the pump.
In this way the engine fuelling is modified.
The PSI box, and other tuning units do not modify turbo pressure.
2) The Steinbauer P-box operates on a slightly different principle. In this case the duration and timing of the injectors is modified. pre- main and post-injections are remapped. The mapping is based on throttle position and engine revs. Thus fuelling does not involve an increase in the common rail pressure. Like the other units the P-box does not interfere with turbo pressure, vane position etc.
Most of the units for sale are now pretty sophisticated devices that work well. Many of the companies, including the PSI box have a long and distinguished record and even offer engine warranties. Some manufacturers, I think Peugeot are one, are offering the tuning boxes as aftermarket options through dealerships.
It is often argued that the units are not as good as a remap. I can't say as I've not tried both. All I will say is that I have yet to see any evidence, other than anecdotal, that remaps are better than tuning boxes. It's about time someone devised a good, objective comparison.
Perhaps someone can answer this question. When a remap is done what parameters are modified and how? For example do you know if and how much common rail pressure, injector timing, turbo pressure etc. is modified? I suspect in many cases the remaps are doing a very similar job to the tuning boxes in order to improve driveability without too much expense with respect to fuel economy. When operated under these conditions, and not with 'pedal to the metal' driving increased turbo boost is not a critical parameter.
In the end it will come down to personal preference. If we're looking for improved flexibility and driveability without worrying too much about 0-100kmh times etc. then I think either a remap or a tuning box will leave you very happy.
That's my 'tuppence' worth!