it was breaking rings all around. never siezed, but piston rings would get welded to the ring inset, and in boost ports.
The rings were getting caught on the exhaust port most frequently, finally solved that problem and the problem moved to the boost ports, those were a bitch to chamfer, so never fully resolved.
I agree that engine was pretty weird revving out, almost like it would explode any given moment when run hard.
There was never any scuffing in the cylinder, however we chipped a bit of the lining around the bottom right side of the exhaust window, and the top left boost port.