My stock tach "floats" (it will oscillates about a 1k RPMs range) once I hit higher RPMs. I was screwing around with the tach to wire up my aftermarket tach and things seemed to work fine before, BUT we were breaking the motor in so we never climbed much above 6k RPMs.

Somone mentioned the Ignition Control module could be bad. What do you all think?

Thanks!

 

check if your distributor is bolted up good