I have a 2014 V6 base-model Mustang (roughly 60k miles), with a K&N Cold Air Intake and Roush axel-back mufflers. Lately I’ve been having issues with a strange form of hesitation when accelerating.
The most common symptom I’ve had is split second hesitation when trying to accelerate by passing a car, but a few times, it has almost stopped solidly in its tracks for a solid second or two, created a popping sound from the exhaust (similar to aggressive downshifting). I’ve run various fuel treatments and cleaners through the system multiple times, tried higher octane fuel, cleaned the air filter, changed to a full synthetic oil, higher-grade oil filter and still haven’t managed to solve the problem.
Would my install of the Intake/Exhaust have compromised the Air/fuel mixture somehow?
Could this be caused by bad spark plugs?
Bad transmission/torque converter or old transmission fluid?
Any suggestions would be greatly appreciated and I thank you for your time.

 

I would remove the throttle body and the AIT sensor and clean them with the proper cleaners. Don't use carburetor cleaner. See if this helps

 

check to see if the K&N requires a tune. A lean condition can be created if you have a CAI that requires a tune and don't tune the car. A/F problems (lean or rich) can cause all sorts of acceleration and drive ability problems.