If you were a kid in the 1980s like me, 225 horsepower was exciting. While today that could mean a turbo four, back then it was a snarling V8 like the 5.0 in a Mustang. It still was good for mid-14s down the quarter mile, so it’s not as puny as it may appear, although the effort to get there was much greater than required from cars of today.

And then came along the 1986 Buick Grand National. The GN wasn’t a new model, but a turbo V6 with 235 horsepower was something to notice, as if finally we had the new-age answer to the muscle car. But Mustangs and Camaros were king (Corvettes were expensive, after all), so no one paid much attention to the Grand National. And then Car and Driver tested the improved GN, and everyone’s jaws dropped:

Zero to 60 in 4.9 seconds. And the quarter-mile in 13.9. Even by today’s standards, the boosted Buick stands out.

All of a sudden, smug Corvette owners began to know what it was like to experience fear. Yet despite the raves, Grand National sales did not shoot through the roof. When the 1987 version came along, horsepower was up by 10, but sales quadrupled based on the fact that this was to be the last year for the RWD Regal and, hence, the turbo Regal; this included the GN and all its variants (the turbo six was available in other Regal models, but always built in smaller numbers). To celebrate the GN’s swan song, Buick engineers concocted the GNX.

Inspired by the 1970-72 Buick GSX, the GNX looked like a basic Grand National but had several differences, many of them subtle:

Functional air louvers on the front cowls

245/50/16 front & 255/50/16 rear tires mounted on 16×8 black “honeycomb” wheels

Fender flares on each wheel well

Analog instrument cluster with Stewart-Warner gauges

Auxiliary transmission cooler mounted behind the front grille

“Improved” Garrett turbo with ceramic impellers and a custom GNX cover

“Improved” intercooler with serial number

GNX emblems

Ladder torque bar and panhard rod for better traction

GNX graphic differential cover

“Improved” hydraulics in the transmission for firmer shifts

Dual exhaust from cat-back with separate mufflers for each pipe

Serialized plaque on dashboard

Horsepower was kicked up to 276 horsepower, meaning mid-13 second sprints down the 1320 was no sweat. Alas, the GNX was created with the intention of the supply not meeting demand—only 500 were planned, but 547 were produced. Many buyers put them away in their garage, never driving them, so it is not difficult to find a GNX with no mileage like this one on eBay. Car #8 has been kept under cover in a private climate-controlled “museum” until the original owner’s recent passing. It sports all of its original crayon markings, paper suspension tags, and even the bar code sticker that never had time to burn off the catalytic converter.

After 1987, the turbo six lived one more year in the 1989 Pontiac Trans Am Turbo, but it’s the GNX that is the king of the 1980’s muscle cars. And the price shows it. For car #8 is currently going for $124,900 with 19 days left to sell.