I just got the Shelby back from PSR. Before any mods they ran a baseline run and got 479.10Hp and 473.00Tq at the wheels. After the install of longtube headers and high flow catted x pipe another dyno ran was made. Recorded 511.05Hp and 501.81Tq at the wheels! About a 30HP and Torque gain with the headers and tune!!!!!!