Even "Low Lead" avgas has a significant amount of lead in it. When they discontinued regular leaded 80/87 avgas and we all had to use 100 Low Lead, we had lots of problems with lead fouling of the plugs. I would imagine you would have a lot of problems with lead fouling in a model engine. It is a common misconception that higher octane fuel, or avgas, is "hotter" or more powerful. The truth is, the higher the octane, the slower the gas burns, and it actually has a little less potential energy.

Good luck
Av8tor