I keep reading posts concerning the different firing order of the spark plugs. Talk of firing one at a time, both at the same time, and more. Could someone explain to me why/when you are supposed change the configuration? why is this advantageous? any downsides?

Thanks in advance

 

Making your leading and trailing fire at the same time will produce more horsepower but will also increase combustion temp. You will need to have a EMS that is very accurate. If the trailing fires before the leading then mostly byebye engine.