Speaking of large pulleys, here's the largest, a 4.00-inch unit that delivered 13 pounds of boost and 904 hp and 721 lb-ft of torque on the engine dyno. That's about 770 hp at the rear tires, which is a bit over what we think is the most fun on the street. In our experience, the newest Mustangs run fast and fun at 700 rwhp. Stepping up 800 rwhp is more wheelspin, white knuckles, and waiting until Fourth gear before hooking up. But you might think otherwise!