It depends on your elevation. 10 lbs at sea-level, I would run 100% 108-114 just to be safe, but I'm more of an err on the side of safety. However, your M8 should have a detonation-sensor, so you can certianly try it, and your sled will let you know if you have premature detonation. At 10,000 feet, you could probably get away with running straight 91-pump gas, but I'd still watch the det-sensor.
I've always been told that av-gas is ok for mild compression increases, but really, if you're looking for the best option for high-intensity applications such as turbo-charging an engine, you should look to race fuel, not av-gas. I don't really know if it's in the formulation or what, but I've lived by it, and I've never melted a turbo down.
