last night i soaked my piston and rings overnight in carb cleaner. didnt really do anything. then i remember a while back you guys talking about sea-foam engine tune up in a can stuff. well i had some from about a year ago (worked great on my old saturn by the way) and i stumbled across it this morning. after soaking for about 1/2 hour, it took off all of the carbon. for 3 bucks a can, its great. just look for the metal pint sized can that looks like its been on the shelf since 1972.