I have the same problem on my 88 TE (185k). At start up after sitting overnight it fires right up but runs as if is only firing on 5 cylinders then smoothes out after a few seconds. New plugs, wires, rotor, cap with no change. Treated with Techron with no change. I am thinking a fuel injector problem but would like to make a better diagnosis prior to replacing all the injectors. The coil is original, could a bad coil cause this type of problem?

Doing some front suspension work now (tie rods & struts), this start up situation is next on my list.

Any ideas would be welcome

Ed