However, you have to add a stronger coil like a Blaster 2. The box alone will do nothing. The whole idea is to upgrade everything i.e., plugs, wires, coil, and the box. I just put one on my tired old 400 with good wires, Champion plugs and a Blaster 2. It ran so much better, I had to turn the idle down. Also, make sure to play with the advance on the dist. It helps to get your "total timing" up to spec. This is usually done with an advance timing light.