A couple of weekends ago I had driven from Azusa down to Irvine (about 45 mins). When I got there, I was letting the car cool down when I heard little popping sounds from the exhaust. Does that mean my car is backfiring? They weren't that loud, but still noticeable (I was sitting in the car, with the door open). All I have is a Cobb SRI. Should I be worried?