As sad as it is it is rarely a tuner fault, i dont know this car or situation but by the sounds of it and the mods a tune should not realy kill it... i mean it would have to be pinking BADLY for a long time to blow up or run lean for A LONG time to blow up. Yet a slight oil starvation at some point in time could have burnt bearings etc and it was just its time..
i dont know, but to be honest unless you heard it on the dyno detonating its head off (or a dead wideband sensor) it could be anything.