3 Series 4 Dr enhance your sedan's look. To get the most bang for your buck, invest in a Nitrous Kit. A good way to update the grocery getting is replacing your 3 Series 4 Dr. A Nitrous Kit can double your horsepower depending on the size of your engine. Overall Style and performance are improved by changing your 3 Series 4 Dr. Make your vehicle much faster with a new Nitrous Kit. Nitrous Kits are the easiest way to add power to your vehicle.