Yeah, it might take a little of both, but if you keep the revs up and don't run to rich it should be ok for a while. I fly a Cessna 172 that has a huge problem fouling plugs during taxi operations prior to take off, so I lean it out for taxi then set my mixture just before being cleared for take off.
When I was using the avgas in my Z with the stock engine it would foul pretty quick, but I think that was due to low compression ratio. If you are running high compression 11 or 12 the avgas will work better, avgas in a stock motor is useless but I love the way it smells when it burns.