It's difficult to say without seeing the car, but I don't think it's the same issue as Chris had if you've got genuine G60 injectors.
Run through the diagnostic guide on here, make sure you check sensor and switch resistances at the ECU connector as that way you're checking the wiring harness at the same time.
Did you check the idle switch was working?
What value is the CO pot set to?
What's your fuel rail pressure at idle with respect to atmosphere?
Did you manage to get your wideband re-calibrated correctly?