If you are reffering to the Accel DFI, there is no limit to the boost level the 'sensors' will take as you say. There is one factor to consider when ordering the DFI, you must let them know what MAP sensor you want. There are three common ones available - 1 Bar (For Naturally aspirated applications) , 2 Bar for up to 15 psi of boost, and 3 Bar for up to 30 psi of boost. There are other MAP's avail, someone was making a 5 bar the last time I checked if you wanted 60 psi of boost.
The problem with using a MAP with a potential greater than you inted is that you lose clarity, because the increment in the sensors output will cover a more broad range.
Even if you were to run 20psi on a 2 Bar MAP, it will not be damaged. But at 20psi, it will output the same fuel as if you were running 15 psi, which may damage your motor unless the fuel map was setup for this.
I can only say get some sort of fuel management computer. It will save you alot of time and money in the long run.