I did the cylinder soak treatment on my 2004 corolla a few days ago. No kreen in the gas tank or crankcase, just 1.5 oz in each cylinder for about 3 hours. The 1.8l engine has 167k on it and has been very well maintained and had no issues prior to treatment - I just wanted to try the stuff after reading about it here. Now the engine is louder, not in a bad way, more like if you replaced the stock exhaust with a performance exhaust. Can anyone explain why that is?