Have a 87 Turbo GT, and for some reason the Tach is acting strange. When I start it up it goes 3/4 of the way around the gauge, (if it wasn't for the Turbo gauge I am sure it would go further)and sits there, I tried rebuilding it from another Tach but same problem. Could it be something to do with the coil? or the wiring to the Tach? Any help would be appriciated

have you tried just pluging a dwell/tach meter to the coil that should give you an answer?

No I haven't , try that this weekend,
Thanks