It could be a lot of things. How do your plugs look? Are they fouling or showing any signs of bad spark? Usually TFI modules just die in my experience. They don't usually go bad gradually. If you're certain that you are getting fuel then inspect your plug wires, coil connector and TFI module connector for corrosion. A bad connection could prevent adequate spark and seeing as you are in a rust belt area don't rule anything out.
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Edelbrock heads, intake, 70mm, e303, 4.10's w/ auburn pro and Compucar.
My 1988 Mustang GT