ZR1X lap 6:49.275 (barely beating the GT3 RS, I'm sure the MR will beat this time soon) http://www.youtube.com/watch?v=ic7qpuJtHK4

ZR1 lap 6:50.763 http://www.youtube.com/watch?v=20oDQHBrWSA

Z06 lap 7:11.826 http://www.youtube.com/watch?v=u1yh7Ptrhwo

They used the American spec Z06 not the slower European one (emissions?).

According to Chevrolet, the Corvettes that performed at the Nürburgring were all U.S. production-spec vehicles with the only modifications being the safety equipment recommended by track officials. This includes a roll hoop, full containment race seats, fire extinguisher, and a six-point safety harness. All three vehicles set lap times for the Prototype/Pre-Production category since the ZR1 and ZR1X are not sold in Europe, and the Z06 was a North American variant.