Two aims I guess. First is to get rid of the deposits and then secondly try to keep it running clean. I would like a better understanding of the implications of having carbon deposits on the piston heads etc and how to keep them clean! My gut says it should perform better if the combustion chamber is clean? Running a Sigma on throttle bodies at about 200 bhp. Engine builder said Tesco Momentum 98 was good. Ran it for a while on that, but then moved to Shell V-power as easier to find Shell stations! Have done several thousand miles in Europe, so used high octane fuel there. Would like to see a test with Terraclean where they check the condition of the combustion chambers etc. before and after the test with a borescope. Tempted to see if Terraclean would let me check the condition after the clean and only pay if it is clean in there! Have always been skeptical about these sorts of products, but used Redex on an 8 year old Honda CR-V I bought (after seeing Jason Plato's 5th Gear video about trying to regain some of the power from an old Carrado). After using it on 4 tanks of petrol my fuel consumption had improved by 40 to 50 miles a tank! Garth