Creamsodauk has given the best advice so far so try that, its perfectly normal for it to cut out when your engine is set for break in.
Dont go messing about with both the needles or youll end up in a hell of a lot of tuning problems !! YES you tune the HSN first when its time to tune the engine but its not time to tune it just yet so dont go adjusting the HSN for now.
Whats needed is for the LSN to be "Tweaked" to allow the engine more air, like someone has already said though, just slight amounts, one to three turns (in 1/8th increments) to the LSN. This will let your engine pull away better, but still expect stalls etc as its running over the top rich for the break in !
Another point (as mentioned above)
The engine needs to be warm (ish) in order for it to work right, so let it heat up a bit, even heat it up before with a hairdryer etc.