Thanks for posting this, Slim. It takes several years to figure out how to deal with possible rule changes. The Sunoco 260 GT Plus is their top grade unleaded. It is being used for engine development this year. The goal is to collect some good data about using this stuff so we are prepared if if becomes the only choice. Also, the ventilation in the dyno room leaves a lot to be desired. If it sucked it would be a lot better than it is now.
It looks like not much, if anything, will be given up performance wise (HP and torque) based on previous dyno testing with leaded vs unleaded mid-octane fuel. The exceptions are cost and fuel economy. The leaded gas gives advantages in these two aspects.