An uprated MAP sensor requires a chip to suit. The ECU reads in a voltage from 0-5V for the MAP sensor signal and a 200kPa standard MAP sensor will read around 5V at 1 bar of boost (2 bar or 200kPa absolute pressure). A 250kPa MAP sensor will read 5V at 1.5 bar of boost.
You can see if you programmed a chip to run 80% injector duty cycle at 1 bar of boost (5V) on a stock MAP sensor, you'd not see 80% injector duty cycle on a 250kPa sensor until you're also getting 5V - i.e. running 1.5 bar. Hence why you need a chip to suit.
As Hayesey said, you lose a bit of resolution in the map as your 16 map points have to stretch from 0-250kPa rather than 0-200kPa, but in practice you don't really notice it! I've got a 300kPa sensor on mine...