What happens when a nearly new Bullitt Mustang lands at HPJ Performance? The answer: a no-holds-barred transformation into a 1,500-horsepower street monster. With only 600 miles on the clock, this 2019 pony car was torn down and rebuilt from the ground up, all in the pursuit of extreme power.

“It’s got 600 miles on it and it’s getting everything,” Greg Connoyer, technician at HPJ, exclaimed at the start of the build. “Hopefully we’re going to be at that 1,400-1,500 horsepower number.”The build was as serious as the horsepower target. To make the extensive modifications easier, the HPJ team literally split the car in half by dropping the entire front subframe and drivetrain. This approach gives them wide-open access to everything, making the assembly cleaner and more precise.

Out went the stock engine, making way for a built RGR 5.1-liter long-block and a massive Hellion twin-turbo kit. To handle the immense power, a TREMEC Magnum transmission with an RPS triple-disc clutch replaced the original manual, sending power back through a carbon fiber driveshaft. The owner had one clear instruction for the dyno session: “Pin the gates shut. I want to see what these turbos will do.”Initial dyno runs proved the car’s potential, immediately overpowering the shop’s roller dyno. “On the roller dyno, we hit about 4,500 rpm. We were at 685 lb-ft of torque already,” Michael O’Grady, tuning specialist for HPJ Performance, said.

After switching to a hub dyno and sorting out a fuel system issue, the Bullitt Mustang finally laid down an astonishing figure: a little more than 1,500 horsepower on 26 psi of gate pressure. To make that power remotely usable on the street, the team installed a Boost Leash controller, allowing the owner to ramp in the boost by gear or by time.

The result is a car so potent that, according to another Scott Martin at HPJ, “You cannot hold first or second gear once it gets there. It’ll go redline before you can comprehend what happened.”

This insane Bullitt Mustang shows what’s possible when you mix boost, a Coyote engine, and a team of professionals who specialize in producing street- and track-capable builds.