MSD stand alone rev limiter

[Nader]

I can't get this MSD "Soft Touch" rev limiter to work with my Marelli Plex ignition. I'm attaching the instructions showing the possible wiring diagrams. I've tried wiring it in using figure 4; engine runs but no rev limiting (using a 3K limit module, or pill). I tried figure 5; and the engine won't run at all, no spark from the coil. I tried those two routes since they apply to a GM HEI ignition, which seems most similar to the Marelli Plex. Any ideas?

[alfaparticle]

I bought a used MSD 6AL on ebay and the rev limiter did not work. I tried switching pills. Maybe it is a common failure mode.