The map on the ecu tells the fuel pump how much fuel to use so if it's mapped for 250cc and you have 315cc it will only use 250cc out of the 315cc tolerance ,
Utter bollocks! If you use injectors larger than the map is intended for, it'll overfuel with the risk of bore wash and premature engine wear. If you use injectors smaller than the map is intended for, it'll run lean with the risk of melting stuff. The ECU has no idea what size injectors you're using, the only feedback on the air/fuel mixture it gets is from the basic narrowband lambda probe which it only uses at partial throttle. On full-throttle the ECU doesn't use this feedback, so opens the injector for a pre-determined amount of time determined by the map tables - it has no way of knowing at this point actually how much fuel it has injected, nor what the air/fuel ratio actually is, so it cannot correct for people putting the wrong injectors in.
037906031D is the VW part number for G60 injectors. The Bosch part number is: 0 280 150 905 - that should also be printed on them.
If you use the resource on this site with the Bosch part number it'll tell you that you have G60 injectors, at a flow rate of 250cc/min (or 255 in this table):
http://www.polog40.co.uk/article_injector_table.php
