We recently had the opportunity to re-dyno our March '09 cover car after it received a raft of bolt-on performance mods.

With a CNC-ported throttle body, a cold-air intake, a fresh AntiVenom tune, a Halltech race-spec air filter, and American Racing headers, the ZR1 made a shocking 613 hp and 582 lb-ft of torque at the rear wheels. That's up from 550/517 in our baseline test.