If you use laquer thinner, just be sure to read the label and get thinner with toluene...some brands use other stuff, and stuff that's not so good for your motor. Maybe a better way to do it is to buy pure Xylene (try a Sherwin Williams paint store, but at $26 for 5 gallons it isn't cheap). Toluene has an octane rating of 114, Xylene has a 117 octane rating. Also, Xylene is one of the ingredients commonly used in octane boosters and injector/carb cleaners.
Check out this website for some interesting comments:
http://www.vtr.org/maintain/gasoline-octane.html