Glad you guys got this all sorted out . Sorry for he radio silence but i'm up at one of our Northern Bases again on a "Management Assignment". I will try this but I originally set out with a flat curve at +40 (70%) and i'm not sure now how I got to the end result.. The LSN is super sensitive and I guess i'm just not trained well in that adjustment.... BECAUSE .. I usually eliminate it. I think the carb might have an issue with the needle/nozzle arrangement. I think the issue is being created but how the jet/needle arrangement meters fuel coming off the Seat.. not optimized for the minute amount of gas needed here.

When i'm back I will have another go - I know this engine will run well as the majority of the range is very good and it runs great otherwise. I have a contingency plan in mind too - I won't build a full on TBI carb YET.. But might build a simple throttle barrel and only run the HSN - Basically mimicking my TBI setup but with an adjustable needle instead of the fixed jet. - no LSN or helical slot easy to do and try.