What underlying psychological conditions does one need to have in order to strap into a 650-horsepower Subaru STI racecar and slide the slick-shod thing between walls at absurd speeds? A strong knock on the head helps, but it’s not as crucial as a good team behind you. Getting Prodrive on-hand to sort out a production-based STI and make it a bonafide GT racer without any restrictions is something to marvel at.

Mark Higgins tried his hand at the event in a production STI back in 2014 and extracted every drop of potential from the machine. Two years later, he got behind the wheel of something a little more aggressive—his TT Challenge car.

Photo credit: //www.klubsubaru.sk

Just take a look at the wheel fitment. Underneath those Dunlop slick-shod wheels are a set of 14″ AP Racing discs, much like a WRC car wears, and the stopping distance, aided by its 2,600-pound weight, is beautifully short.

The rear wing also aids some of that braking performance, but it can reduce its angle of attack on the straighter sections of the course so that the brickish WRX body pierces the air and finds a higher trap speed. To provide the needed thrust on those long, flowing sections at the Isle of Man, Prodrive tuned the 2.0-liter motor to make 650 horsepower. Somehow, they’ve made that 650 horsepower easily accessible, and with different gearing to suit the powerplant—which revs to an astonishing 8,500 rpm—Higgins can lean on the engine’s torque and shift less frequently than he had to with the previous configuration.

Paddle shifters also give him a little added control when managing the car over bumps, of which there are many at the Isle of Man. His steering inputs remains relatively calm despite the pockmarked surface of the road—it is used by trucks and normal cars as well, and it’s far from a billiard table-smooth surface. However, he still hangs it out on occasion; the power is enough to ride the car sideways out of most corners.

Top speeds and walls aside, dealing with the constantly-changing surface is another challenge specific to the Isle of Man.

Plus, the combination of big power and longish gearing means he’s able to nudge 180 mph between stone walls. How does a man manage to nip the hay bales at those sorts of speeds? Well, intimate knowledge of the track helps, and since Higgins, a Manxman, grew up there, he’s more than familiar.

Familiarity is only useful when complemented by a healthy dose of precision and courage under pressure. One of the fastest and most daunting sections of the course directly after the start-finish line. The bump at the bottom of Bray Hill nearly claimed Higgins back in 2011, but with more downforce and horsepower, he was much faster in 2016—brushing 170 mph—and the car never skipped a beat.

That section isn’t the fastest however, and as Higgins approached some of the bumps on the flat-out sections of the course, he needed to exercise a little caution. With those speeds and the design of the Subaru, there was always a chance it could get airborne (4:45) and continue flying. A little circumspection helped, but not too much. Since straightaway speed is all-important and the the course is litter with blind, late-apex corners leading onto straighter bits, it takes some trust in his own ability and the car’s poise. However, that doesn’t mean a psychologist would have a good time looking into this man’s head; he’s certifiable.