I have done some more digging and it seems if you go with an ECU setup you will need to protect both the coil and the ECU. Hence the ballast resistor comes to the rescue.
I have the MSD Blaster 2 coil which has a .700 ohms resistance in it already. This is why MSD will sell you a .800 ohm resistor for a total of 1.5ohms which would put you at 8 amps for a V8 (acceptable - read below). So (for example) if you have a stock 1.2ohm resistor with a MSD Blaster 2 coil then you are at a total resistance of 1.9ohms which would affect spark. You could swap out the ballast resistor for one that is .8ohms and should have better performance and longevity.
Ymmv,
B
This is a good read for those wanting to know:
What type of coil can I use with the Ignitor™? How do I check my coils resistance? (12V negative ground only)
To determine if your systems coil is compatible with the Ignitor, some measurements should be taken prior to installation of the Ignitor. Caution… While performing this test, never leave the ignition switch on for more than 30 seconds at a time.
Set your voltmeter to a 15 or 20-volt scale. Attach an 18 or 20 AWG jumper wire from the negative coil terminal to an engine ground. Attach positive (red) lead of your voltmeter to the positive side of the coil, and the negative (black) lead to an engine ground. Turn the ignition switch to the run position. Now read the voltage at the positive coil terminal. Turn the ignition switch off. If the voltage measured is approximately 12 volts, no resistance wire is present. A typical resistance wire will provide 9 - 6 volts.
The next step is to determine the resistance in the primary ignition. Label the wires attached to the coil terminals and note their appropriate location. Make sure that the ignition switch is off and disconnect all wires from the coil. Adjust your meter to the lowest ohm scale. If you are using an analog style meter make sure to zero the needle.
Measure from the negative terminal to the positive terminal. Write your measurement down.
Now the maximum system amperage can be determined, divide your voltage measurement by your coil resistance measurement. This will give you the system current or amperage.
Four and six cylinder engines should not exceed 4 amps. Eight cylinder engines should not exceed 8 amps. If the total amperage in your system is higher than the amount recommended for your application, you should install a ballast resistor.
Example
Voltage 12
Resistance 1.5
12 / 1.5 = 8
Total amperage 8
