I'm installing a zx9r e that came without a loom/ecu. Do I need a zx9r e loom/ecu or can I use a earlier equivalent.

I think the ZX9E's don't have the cam position sensor so that may cause problems using an earlier loom wired for that sensor, especially as an earlier ECU will be looking for the sensor (and from experience a missing/defunct cam sensor stops all attempts to get it running!)

I don't know if the E can be retrofitted with the sensor as the position only seems to be blanked off? (I've only got pictures to go on)

IMHO, easiest option is to go with the E model ECU.