I installed this on my 2017 Mustang GT and am happy with the power and sound. I have not had a chance to check the gas mileage. I am concerned that the car has vents in the hood to let the engine heat out and one of the vents is directly over the air filter. If I planned to have the car set outside in the rain, I would remove the cold intake system and reinstall the original system before the K & N filter gets soaked and possibly lets water into the engine.
Worth the buy.
I have a 2013 Ford Mustang with performance ignition coils,cold air intake,tuned length headers and a performance tune. The throttle body spacer was very easy to install. After install I drove the car around and noticed that the you can hear the engine sucking in air. Before you didn't hear anything. Also I felt a little more throttle response.