Did you ever get to the bottom of this? I have a 2004 1.4 golf coming back in next week, retrieved these codes today-
16645 injector cylinder 1-N30 short with ground P0261 intermittent.
16651 injector cylinder 3-N32 short with ground P0267 intermittent.
16654 injector cylinder 4-N33 short with ground P0270 intermittent.
16648 injector cylinder 2-N31 short with ground P0264 intermittent.
17833 EVAP purge valve-N80 short to ground P1425 intermittent.
17525 O2 sensor heating circuit bank 1 sensor 2 short to ground P1117.
16517 O2 sensor bank 1 sensor 1 response too slow P0133.
16523 O2 sensor bank 1 sensor 2 response too response too slow P0139.
History - starts ok when cold, sometimes won't start when hot. Was thinking a wire or sensor shorted to earth but the above relay suggestion seems to make sense (low voltage not short to ground) & I've had problems with solder joints on these relays before.