Here is a document that I found once about that.
This is true with a CD ignition like MSD, Mallory And Crane sell or with any ECU that is internally regulated(like GM HEI or Pertronics). According to MSD(this is not me making this stuff up) the Mopar boxes are not internally regulated and need to have a total resistance (coil primary + ballast) of at least 1.5 ohms. The Blaster2 coil has .7 ohms of primary resistance and comes with a .8 ohm resister for a total of 1.5 ohms. MP's literature on ballast resistors is confusing at best and many catalogs and advertisements incorrectly state that an Orange box and Blaster2 coil can use a .25 resistor. Maybe this is one reason the Orange box has such a bad reputation.
The .25 resister is for racing with a chrome box and a 100 wind coil equivalent to the blaster2. Use under 3000rpm should be limited to less than 30 minutes to avoid overheating the ecu. With no resister it would overheat even faster. Just like the orange box, for street use a .8ohm or more resister is necessary.
