I think that this is a problem with the earlier RS focus' that had the original AE map which is regarded as a better map than the later AF map which had a lean spot. The problem with the AE map is what you have just stated in that for cold starting it can be slightly erratic but that is just a characteristic of the map. I think the only way round this is to have the map tweaked by somebody not a generic flash map as the problem will still be there.