Alcohol does have less BTU's per unit than gasoline, but it doesnt detonate at high compressions like gasoline. With more compression you get more air/fuel in the combustion chamber, make more power. Plus alcohol and nitromethane require much less oxygen to burn per unit so you can pack much more fuel than air in as well, giving more power yet. Im not an expert so there Im sure there is more to it than that. Running straight alcohol requires a different carb setup since it needs to flow over twice the volume of fuel compared to gasoline, and as far as fuel systems go, if you are playing on that level, having a fuel system only last a couple years isnt the end of the world.