We recently tuned a 2013 GT500 here at Steeda Autosports whose only modifications included a 10% overdrive pulley, Kooks Long Tube header system with high flow cats, and a touch of our custom dyno tuning. The difference? An additional 96.7 horsepower and 90.34 ft/lbs of torque at the wheels! Here is the dyno sheet. Needless to say, this car is now much more fun to drive! While the peak to peak torque gain is 90 ft/lbs, from 4600rpm to 6200rpm the torque difference is well over 100 ft/lbs through that particular range!