If you are referring to their aftermarket "white box" replacement 86-87 Magnavox module, it does not generate a tach signal at the green terminal. If you look at the current information on their website, it does state this.
http://www.nos4gn.com/servlet/the-44...l-parts/Detail
While it is a great bargain replacement part, and appears to be very reliable, it does have this one deficiency. I don't believe there is anything you can do to "fix" it. Using an AC Delco part, or an alternate brand that does not have this issue is the only alternative. Not all have been deemed to be terribly reliable. Also, I believe the Borg-Warner / BWD units have been noted to have a similar deficiency in the past.