It sounds fairly typical for a version 1 engine .
There are a few thing to do to improve it . some of which you have already done- but I will note the steps in the order I use.
1) Use an NGK CM6 plug gapped at .024 (throw the original plug in the trash)
2) Check and verify the ignition timing is no more than 35 deg BTDC ( 28 to 32 is recommended) , some are incorrectly set at the factory.
3) install a vent tube and line on the diaghram vent cover plate of the carb. run the line in to the fuselage away from irratic pressure changes.
4) Be sure the prop is balanced correctly (don't assume it is, ever)
5) make sure the engine is mounted securely to the firewall and the wing(s) are on the plane when running the engine (this helps to dampen and stabilize the engine and does make a huge difference in how the engine runs and how it is tuned.
6)readjust the low and high end needles to 1-1/2 turns out each as a starting point .
7) warm the engine up thoroughly 5 to 10 minutes at 1/2 throttle prior to attempting to fine tune the carb .
Peak the engine rpms at WOT with the H needle
idle it down as low as it will go reliably and lean the L needle , the rpms will rise-then lower the idle speed and lean again. keep doing this untill the engine will not idle reliably . then open the L needle 1/16 turn at a time untill you get a good throttle transition and a reliable idle. Do not open the L needle any more than needed to get a good transition from idle to WOT as this will also effect the mid range and make it rough .
Peak the RPM's with the H needle again. do not go over rich untill the RPM's drop - get max RPM
Note : After tuning the engine Keep the idle speed as high as you can and still be able to idle down for landing and ground handling untill the engine breaks in some , the engine will idle better and have more power as it breaks in with Several gallons of flying time .
You may need to go to a lower pitch prop during break in . I recommend an 18x6 or 19x6