I have my S2 in for annual inspection and the mechanic noticed an area of carbon in three cylinder barrels. The compressions were all good 76/80 to 78/80. He then found small leaks at those sites and cracks upon further inspection in 3 of the cylinders. Also one of them was porous with leaks in multiple places! This is after a total of 162 hours ! When he called TCM they did not seem interested until he mentioned the porous cylinder. They then agreed to replace all four of the cylinders. I have had good oil temps (under 200 degrees) and rarely lean unless flying above 5000 ft. It seems that TCM continues to have quality control problems but at least because of all of the previous cylinder problems people have had, they are willing to replace them even 5 days after the warranty ran out.