For the final year, 1987, Buick introduced the Limited Production GNX "Grand National Experimental" at $29,900. Produced by McLaren Performance Technologies/ASC, Buick produced 547 with the Grand National interior trim Package. They were then sent off to McLaren Performance Technologies and upgraded into the Buick GNX. Buick underrated the GNX at 245 hp (183 kW) and a very substantial 360 lb·ft (488 N·m) of torque. This was created to be the "Grand National to end all Grand Nationals."
Changes made included a special Garrett T-3 turbocharger with a ceramic-impeller blowing through a more efficient and significantly larger capacity intercooler with a "CERMATEL (Ceramic/Aluminum) coated" pipe connecting the intercooler to the engine. A GNX specific E-EPROM, low-restriction exhaust with dual mufflers, reprogrammed Turbo Hydramatic 200-4R transmission with a custom torque converter and transmission cooler, and unique differential cover/panhard bar included more of the performance modifications. Exterior styling changes include vents located on each front fender, 16 inch black mesh style wheels with VR-speed rated tires, and deletion of the hood and fender emblems. The interior changes of the GNX included a serial number on the dash plaque and a revised instrument cluster providing analog Stewart-Warner gauges, including an analog turbo boost gauge. Performance was measured with a quarter mile time of 13.2 seconds at 104 mph (167 km/h) and a 0-60 mph (97 km/h) time of 4.7 seconds.
Source: Wikipedia (original)