Just had a quick think about this and had the following thoughts:
1. The cold start injector may not be firing? This sort of makes sense if it is only struggling to start on stone cold start-up. Check the 5th injector, make sure it's plug is connected, and make sure the sensor on the back of the head (the brown one I think?) is plugged in and working as this tells the ECU when it's cold enough to fire the 5th injector.
2. The coolant lines running to the wax pallet on the throttle body I assume are still hooked up?? If it is on your GTZ I am guessing they will be as that beast does not appear to have been tampered with.