I had a similar problem, my 87 Formula would run for a few seconds, and stall, restart would run a little longer, It would stall several times before it would actually start to run ok, but the idle would be unstable. Finally, when it was warm, it would begin to run really well.
Turns out it was the temperature sensor on the front of the intake. Paid $13.00 for the sensor and I no longer have the problem.
87 Formula 5.1 converted to TPI Yellow/Black
SLP cam, headers, cat-back exhaust
Ported & polished TPI intake
Gil Younger (no yo-yo) Shift Kit
3.73 Posi gear
Baer 12" brakes 4 wheels
Hotchiss strut tower brace
South side machine frame connecters
Custom reinforced control arms and pan hard bar.
Custom Leather interior