[JL8Jeff]

Some form of a top end cleaner like Seafoam or GM TEC will help clean out carbon deposits and make the engine run smoother and will allow you to pick up some power and mpg. Sounds like that is what Sears is offering. But a nice, hot ignition system will also clear out that crap and stop it from reforming. The biggest danger is if there is too much carbon that gets blown out and could clog your cat or mess up your O2 sensors. As for the hydrogen thing, I'll wait until an unbiased person tests it out. With the mineral content in our water I can't see that working too well for very long.