I was just given a case of this stuff. It's marked "not legal for sale in California," which translates (to me) as "actually effective for it's intended use." Apparently, it is very effective for removing carbon deposits from combustion chambers. It is supposed to be poured down the carburetor or ingested through the PCV hose (fuel injected vehicles) until the engine stalls, and then let it sit for 15 minutes (I'm paraphrasing the instructions, since I don't have a can of it in front of me right now). I tried the BITOG search function, but didn't find much. Anyone familiar with this stuff? Any actual experiences?