Super tuning car runs good shooting for great

I gotta wonder if it is:
- A grounding issue.
- Or perhaps the phasing of the reluctor output in the distributor is reversed from what the MSD wants to see.
- Or maybe your timing light is responding to different pulses in the MSD spark chain. As in: it triggers on #1 pulse in a spark sequence, then #2 pulse in the next cylinder's spark sequence, and so on. I think MSD has some tech info on timing lights on their site.