"What is the deal with Acetone? How do you use it and where to buy?"

Theoretically it increases the 'energy content' of the fuel (basically the opposite of ethanol). May even get more than 0.1% increase in power - sorry, couldn't resist

I suppose that it would also tend to keep all of the fuel system clean as a whistle too.

Personally - Acetone anywhere near plastic & rubber components scares the crap out of me.