Thanks for the update on the triples.
Went out for another ride this morning, and the start up is much better. Just does a kind of cold start warm up procedure for a few seconds but then drops down. Before was too high and too long and I believe it was due to the plenum not seated properly. If I turn on when engine is warm, goes to correct idle more or less immediately.
The beast has been tamed! For the time being anyway.
Your time and patience is much appreciated.