Ran,
The cylinders had over 700 hours on them (most TCM only get 500), and was fouling the lower plugs - cylinders 1 and 4 if I recall correctly. I had to clean the plugs before almost every flight. They were also subject to AD 96-12-06 which limited the timing to 24 degrees. The ECI jugs fixed all the problems, haven't had any issues with them. I burn auto-gas, so I didn't up the compression with different pistons.
Tony