My limited understanding of a ballast resistor is that it reduces voltage across the 2 contacts and in the process produces heat. So I got a replacement resistor from Advanced Auto (Carquest brand) and used it for a while. Bought a NOS ballast resistor on EBay to replace it and noticed that the NOS resistor was a little thicker and a little longer than the Carquest resistor. I'm wondering if this small difference could effect performance. Paul