Dennis,

As far as I know it is just the standard 120SF YS part number 0070. I am not familiar at all with YS engine as this is my first one, specially the older ones. I would go with the 20% nitro, I know it is more expensive (15% @ $12.50 vs 20% @ $14 per gallon), but I got about 300 more RPM than I had with 15%. Try a 16x6, 16x7, or 15x8 on your 110, it might be a little happier, and on 20% nitro....
Andrew