I realize this is old news but for anyone that hasn't caught it yet, here is Tadge's comments regarding what went wrong and why the Z06 didn't finish:
http://jalopnik.com/why-the-corvette-z06-flunked-motor-trends-big-performan-1736976325
http://jalopnik.com/why-the-corvette-z06-flunked-motor-trends-big-performan-1736976325