I think what richard is saying to you is that he would need that car for that period of time to go over a range of things like the actual hardware associated with the running of the car.
Several times I have had a 'bad tune' only to find that later down the track it was hardware related. Im not personally having a go at you but too often people blame the tuner for hardware misgivings.
However this does sound like a cold start tuning issue, this take time to sort out, but if Richard takes his time and goes over the tune and the hardware you should get a good result