The low needle on my 49 is pretty sensitive. A slight tweak in or out can make the difference between an engine that transitions perfectly and one which sputters or dies. I think it may be vibrating out slightly in flight.

I generally tune this one based on how it transitions from idle to WOT. If it sputters I lean the needle; if it shuts down I richen. The engine is pretty new, thought - I'm hoping that things will settle down some once I put some more time on it.