They failed a lot on GM's back in the day. If an HEI GM wouldn't start it was the module 90% of the time. The new modules came with a small packet of dielectric grease. I don't know what the grey goop is that you used.
Or the rotor got burned through. :D
The grey goop is the same heatsink compound I use in our HEI kits. (for computer processors)
There is white, grey, silicone based, ceramic based and a few others.
They are all thermal paste that transfers the heat from the ECU to the heatsink. (not dielectric grease)
