[petbeemer]

Pictured here are a set of Evo 3 pistons which are known to break ringlands.
This is a set of 4 pistons from the same engine,if you look close you will see carbon deposits all around where the rings sit but there is also a clean bit,where the clean bit starts and finishes is where the ringlands have cracked, this usually happens on the thrust face of the piston and generally makes the piston useless.
For some reason when Mitsubishi made the Evo3 they decided to up the compression from 8.5-1 to 9.0-1 probably to help with power off boost and to get the engine to spool the turbo quicker,in re-designing the pistons they also made changes to ringlands making the edges sharper and the gaps tighter causing 'ring flutter' which in turn causes ringland breakdown.
Symtoms are hard to spot as compression is rarely affected nor is oil consumption and generally the engine will run fine until more power is needed,but if your planning on rebuilding your Evo3 motor then budget for a set of pistons