The piston rings could be scoring the bores of the block if they are damaged, only takes a split second and one rev to damage them if your unlucky.
If part of the piston ring has detatched where has it gone? has i been crushed up and gone into the cylinder? iof so has it damaged the valves and the heads? etc etc
untill a full engineering report is done to ascertain whats damaged and not you wont have a full picture, it could have done a ring land, could have done a piston itself, etc etc
At the min all you know is its burning oil and theres oil where it shouldn't be.
full stand alone ecu system, if your having it rebuilt then id go that route so you can sack the maf off etc