Try running it right at the 2/4 stroke break to where it's running rich 2-stroke most of the time with the occasional miss. Do this for maybe 24oz of fuel. Let the engine cool down and flip the prop briskly through compression a few times. See if it improves. If it doesn't, try scuffing the bore with 400-600grit emery paper to make a cross hatch scratch pattern and re-break it in.
Back to to the questions I asked earlier - what did you do to prep the liner before installing the new ring and how have you been running it to seat the new ring?