Okay!!! Problem resolved.
I still have not hooked up the adaptor but I did check all of my connections and even sanded the area my ground was hooked up to so I was sure I was getting a good ground. Still same problem.
Soooo I connected the Tach Adaptor just using alligator clip jumpers. One side to the hot on the battery to simulate the switched hot. The other side to the negative side of the coil.
Despite the genius at Mallory insisting it would not have any affect on the Tach it solved the problem.
Now just for a little time to find a good spot to mount it and run the wires in a stealthy way!