[mr0077]

Okay, Art,
here is what I'm coming with from the fog of 3 years ago...looks like I had the std ERA wiring hookup, but with the help of ERA, I finally figured out to wire from the MSD box tach output directly to the signal terminal on the back of the tach...of course, this was AFTER I bought and installed the tach adaptor...LOL!!
Anyway, try wiring directly from the tach output on the end of the box away from the big power cables, directly to the back of the tach...worked for me.
Good luck