This is seems to be a common problem. Does it surge; ie, drop low in the RPM then try to recover then die? When this happens to me, I restart the car and it will idle perfectly. I have never found the solution but when I added multispark COPs, it seems to really help. Still will happen but not as frequently. I've talked to BOE and they have not been able to find a root cause but have also tried a couple of solutions that seemed to help. It acts like a vacuum leak but goes away right after starting. So, my best guess is that it is a sensor that starts giving erroneous data to the ECU. After restarting, the ECU uses a new value for the sensor and it is happy again. I just do not know the ECU code well enough to determine which sensor could cause this symptom.
Good luck and let us know if you find something that works for you.