Why is it needed, I have Nokya bulbs and I burned 2 ofthem within like year and a half, which I think is pretty normal. What will I gain by upgrading the harness?

 

You only need the upgrade harness if you're running higher than stock wattage bulbs..ie 80/100watt bulbs. What it does it prevent your bulb sockets from over heating causing them to melt and also it's used to make the higher wattage bulb perform to it's maximum capability, which I think isn't that big of a difference than stock, however it is a noticable one.