Indeed, that's why I am looking for someone local who has done it. I did manage to get rid of most of the stumbling, simply by wiring the exhaust valve open. Sounds a bit better and I have noticed no loss in power.
This had no effect on the 3000-3500 rpm lean spot. So, obviously still much too lean, even at this altitude. I can't imagine how much worse you all have it at sea level.
If I come into money I may consider the race ECM. Good suggestion.