Not really sure what the problem is??? So about a month ago my car started acting up, and the exhaust would backfire sending a huge cloud of black smoke out the rear, and all power to the car would be lost while I was driving down the road...it stopped doing this, and only did it like 4-5 times within two or three days...but the question is that ever since this happened my gas mileage has dropped from around 33mpg to around 23mpg...any ideas of what could be causing this to happen to me....Thanks....