Ok so I have 2015 mustang with 2000 miles on it. Recently I thought my car was louder in the exhaust but wasn't sure until my son who live's with his mom noticed it last time he was over. I received car with 20 miles on it and I have really babied it till it was broke in. I always felt like when I accellorated it was really hesitant. It is a base model with automatic and I just had a powered sub installed and they disconnected the battery and when I picked it up it was a lot more responsive due to battery being disconnected, I believe something like throttle sensor was reset.its actually a lot more responsive I believe due to this. Has anyone experienced anything like this.

 

It's called a computer relearn. This happens when the battery is disconnected for a time

 

You made your car think it is a 6 cylinder the way you drive it. The computer is telling you that you need to use a little more go peddle