Q: I purchased performance brake pads and rotors however I only have a front pair of rotors.. 2014 Ford Mustang

Hi there - while there may be a very slight performance gain to be had by also replacing the rear rotors, you will be fine without doing so unless the rear brake rotors are severely grooved or otherwise worn. The rear brakes contribute 40% or so of total stopping power, so optimizing front brake performance will accomplish the greatest improvement. For professional assistance with this repair, I recommend brake replacement performed by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, and give you an accurate assessment of damage and cost estimate for repairs.