The ZR1 was stock.
http://blog.gmnext.com/?p=194"The car was bone stock with the exception of the communications and safety equipment. The tires were production Michelin Pilot Sport 2’s. These tires have been developed specifically for the ZR1 and will have impressive wet traction and wear (tread wear rating = 220), in addition to excellent dry road holding. Chassis alignment and vehicle height were set to factory specs. Likewise, the engine calibrations were absolutely stock, emissions compliant and the car ran on pump (not racing) fuel. The vehicle was exactly like the cars that will be built in Bowling Green, Kentucky and sold around the world later this summer."