RE: Improper break-in
when I first ran my OS 46AX for the first few flights and run in there was always some dark/black slime in the exhaust oil,as it became more broken in and I leaned out the engine it seemd to go away and I have not noticed any for a while.
one thing I did do was switch to a OS#8 plug when the stock one wore out it seems to run smoother and idle better.
the #3 is cheaper and is a little hotter temp.