So this is my first time owning this gen of Mustang (S 197). I have new coils MSD and new motorcraft plugs. I feel I get a misfire at low RPMs when accelerating. Hear it good in the exhaust too as I have muffler deletes. It was doing it before I added the cold air kit and underdrive pulleys and tune. There are no codes and no check engine light. Thanks in advance.