JMHO, most of the failure troubles associated with MSD units (or any for that matter) can usually be attributed to wiring. And usually it's bad connections, undersized wiring and/or grounding that causes the problems. Grounding is usually one of the biggest problems because people just can't believe a ground can cause trouble, however in sensitive electronics it's crucial. MSD boxes not only produce multiple sparks at the plugs, they generate higher voltages at the plugs as well. And why I ground my heads, the last thing you need is that voltage going through the distributor module into the box (POW).

Personally, I star ground everything on my motor (heads, intake, distributor, alternator, A/C compressor, exc) with wire sized to match the loads applied. I don't like the idea of current traveling through the motor (especially alternator current) and its moving parts. Check out the grounding on new cars and you'll see how many grounds they use to protect the electronics.

If in doubt, GROUND it out....