i have a similar story mate, i was thrashing my missus xr3i down the m5 when the oil press light came on followed by loud tapping, i also took head off and everything was fine but when i dropped sump and took big end caps off the shells were like tin foil! scored crank as well so it was an engine out job. the car had done about 90,000 which i think is the reason it died when abused. if yours has done 160 odd thou on same shells then i think there is a good chance your race killed off the bottom end. hope you get it sorted mate.