I keep wondering why people will go from 100LL Avgas to 95 Mogas?
Just because engine manufacturers say you can use a minimum of 95 Ron fuels, doesn't mean this is the best fuel to use.
98 Mogas is still a lot cheaper than 100LL (if that's the reason to use Mogas).
A lot of the Avgas fuels, specifically in aero engines, often caused run-on, this being the reason most aircraft engines use an idle cutoff, rather than just killing the mags.
But more to the point, run-on is more likely to be caused by engines being run hotter than they should, in conjunction with carbi's set up a bit lean at idle?