Denis,

Usually, if the midrange of the engine is too rich, then the idle mixture will need to be leaned a bit. This will require you to raise the idle RPM a bit and reset the high-speed needle. You should be able to eventually get an adjustment that will work nicely.

Don't worry about raising the idle RPM a bit. The idle RPM you're getting would be considered on the extrememly low side. We normally idle the engine at about 2,200 RPM or so. This insures a good transition.