A vehicle that is Fuel injected is already optimized in both the fuel delivery and the spark delivery. Since the ECM controls spark there is no need for any kind of Multiple Spark device IMHO. I had/have an MSD 6A box and cannot tell any difference with or without it hooked up. A vehicle that doesn't have an ECM to control spark will benefit from the MSD box in that it will give you a longer duration of spark to help burn more of the fuel in the cylinder and give a smoother idle and quicker starts.