The GNX is legendary for its staggering performance; yet all this power comes from an efficient, turbocharged 3.8 liter (231 cubic inch) V6 engine. Modifications included replacement of the stock turbocharger with a special Garrett hybrid unit featuring a super-lightweight ceramic impeller, the first of its kind. The decreased impeller weight allows the turbocharger to spin up much faster, dramatically increasing performance while decreasing the turbo lag or spool time inherent in most other turbocharged engines. Maximum boost was set at 15 psi and the turbo also incorporated special dynamic turbine shaft seals in the center housing rotating assembly to reduce drag on the shaft. The turbine housing was redesigned to include a contamination trap to keep solid particles away from the turbine wheel and help prevent excessive turbocharger wear. Also installed was a more efficient Garrett air-to-air intercooler with a higher fin count for additional cooling capacity and better vehicle performance. The intercooler to engine pipe was coated with a special ceramic/aluminum compound for increased heat rejection and dissipation, helping ensure a cooler and denser charged air feed for the engine. Functional vents were installed on the front fenders to pull heat away from the engine while driving to further cool underhood temperatures and enhance performance.
To handle all this extra power, the Turbo Hydra-Matic 200-4R transmission was beefed up for increased hydraulic pressure and modified for firmer shifts. Also added was a special front-mounted auxiliary oil cooler to lower fluid temperatures, thus enhancing the efficiency and extending the life of the transmission. The Engine Control Module (ECM) was recalibrated and reprogrammed with an exclusive GNX-only management chip. The factory single-muffler exhaust system was replaced with a completely redesigned freer-flowing dual-exhaust system with two low-restriction mufflers that were modified to clear the special suspension.
All of these modifications added up to 300 bhp and a stump-pulling 404 lb-ft of torque at 3,900 RPM, propelling the GNX to a then unheard-of 13.2 second quarter mile time.