You didn't mention what type of ignition you are running. I have an MSD system. When my MSD 6AL box started going out, it exhibited similar symptoms. I bypassed the box to verify the problem before replacing the it.
PANTERA INTERNATIONAL
A DE TOMASO CAR CLUB
Presents the De Tomaso Forums
The On-Line Meeting Place for De Tomaso Owners and Enthusiasts From Around the World
Clicking on the banner will take you to the sponsor's website.