I have a MSD in cab spark retardig control unit, uninstalled. As I have no pinging with 87 octane I am having doubts as to the need for this device. Any suggestions?

Is it an 8680? It is used in conjunction with the MSD 6A or 6AL ignition unit. The combination allows you to adjust the spark for the load, hill, temperature or gas quality.

I use one and like it.