Roush is readying its most powerful Mustang offering to date. Starting Saturday, Sept. 1, customers can pre-order the 2019 Roush Stage 3 Mustang, complete with 710 horsepower and 610 pound-feet of torque. The RS3 Mustang utilizes a new "Phase 1" TVS R2650 supercharger, which is based on Eaton's R2650 rotating assembly and improved with a new front inlet. Compared to the previous, 2015-introduced car and its R2300 blower, the Mustang can coax an extra 40 horsepower from its 5.0-liter Coyote engine thanks to the improved supercharger. Just as a reminder, a stock Mustang GT has 460 horsepower; the Stage 3 gives the car 250 extra ponies. That's about a Focus ST's worth.