"Under certain harsh driving patterns, specifically when repeatedly or continuously operating the engine above the red-line (RPM above 6,700), abnormal combustion could occur resulting in serious internal engine damage in the form of broken piston ring lands. This abnormal combustion condition is the result of an over-lean fuel mixture caused by a combination of fuel cut activation and high turbo boost. To prevent this condition from occurring, Subaru has developed a modification to the Engine Control Module software logic that will improve combustion management above red-line engine speed. This revised logic will not adversely affect peak vehicle performance."
That was the problem with STIs. TSB WVE-15.
