This is the Stunt Car from the opening scene of Fast & Furious 4, where Dominic Toretto uses the car while hijacking fuel tankers in the Dominican Republic. Dominic drives up beside the fuel tanker, while Letty jumps onto the tanker. She then uses a nitrogen spray gun and a hammer to unhook two of the tanks while Dominic drives the Buick in front of the tanker to slow it down.
The production team built 8 of these cars, and installed CNC slide brakes and Wilwood calipers in the rear to help facilitate stunt demands.
The most unusual of the seven GNs built was one with the body mounted backward on the frame so it could be driven at speed while appearing to be going backward. To get the engine tucked under the trunk lid, however, the turbocharger and its plumbing had to be removed. Most of the other GNs retained their original turbo V6s, though a couple had Chevy crate V8s installed.