Carburetor, MSD, Holley Sniper EFI questions

Please post links to the documents you are referring to. However, most of these aftermarket EFI systems are designed to function with many different ignition systems

There is a VAST difference however between some ignitions

Older Breaker points (Kettering), the Mopar breakerless, and GM HEI function sort of the same. That is, they switch the coil NEG to ground, and open that connection to make the spark

The MSD or and other CDI (capacitive discharge) is a whole different animal. Those systems charge a big capacitor, much like a photoflash, and the trigger causes the circuitry to discharge that cap into the coil in the form of a high power pulse. MSD is just what it says Multiple Spark Discharge.

An important difference between MSD and any other switched igntion is that you CAN NOT trigger off the coil. Nothing at all should be connected to the ignition coil with CD/ MSD EXCEPT the two coil wires from the ignition system

A trigger for other purposes such as the EFI must be done according to the individual EFI destructions