403's are the bosch grey injectors, but you will only find out what bhp it is capable of, if you know the rest of the set up it was intended for, i.e. cams compression ratio, turbo and so on.

some of these could be figured out if the ecu was calibrated for the engine you got, but there is no way of knowing if it was

The best solution would be to find out what is fitted to the engine, and then get a new chip from any tuner for that spec, or at the least yuo could find out what bhp the whole set up would make, not just the ecu