Ray,
I always send everything stock engine came with.
Check valve, prop nuts, needle valve, stock muffler with pipe >> In case they run the engine to test. I know they have spare parts, but I don't want to bother them because they have many other engines to test also.

I think the description of problem(s) is a must, so that they can work on it quickly.
Last time, I had my YS91FZ returned within a week.
I live in Idaho, so Nevada is not so far.

I always ask first before shipping out the engine.
Hope this helps,