I actually filled my air ports with hot glue, let it dry, and put it back on. Worked just fine.
I was running 12* with my Nutter. However, my Carter carb took a crap and was causing me all kinds of issues. So I put it back to 8*.
I would re set your timing the correct way and see what you get. I may actually bump mine back up to 12* BTDC this weekend after I change the oil.