How old is your engine? The original O.S. Max .46 FX-H had a difficutly with being a bit lean in the midrange, near the hover throttle setting. This was fixed by O.S. 1997, one year after the engine was introduced.

If your engine was purchased after that, it has the "new" carburetor, which has been unchaged since.

What difficulties are you actually having? Your note doesn't say.