I've always preferred Mopar cobustion chamber cleaner (MCCC). DSMer's generally consider it the most effective cleaner to use.
I took out my spark plugs poured this stuff in then let it sit over night. The next morning I took out my EFI fuse, put a big towel over the top of the engine and cranked for a minute off and on to see what I got. :ugh2: UNBELIEVABLE :ugh2:
The stuff that comes flying out of there made me thankful for the big towel I put over the valve cover. I started up the car ran it around the block as it started to clear up and stopped smoking. I ended by changing the oil and spark plugs :bigthumb:
i have used this on my Supra (83k miles) and my civic (140k miles). works great in both cases. keeps the emissions clean as well as ups mileage. my supra got al ittle more mileage after i used it once, im expecting a better gain after i use it again next oil change. makes the cars run smoother, very highly recommend it for the 5 dollars it costs.