Ok boys and girls here is a good one for you.
I worked on an '88 TPI all morning trying to find a hesitation and stumble.
After changing many parts back and forth and gaining nothing, it still would go lean and stumble, I said what the heck that is a aftermarket ignition coil, I wonder....so I changed it and wella!!! problem went away.

So I changed it back, problem came back.....
I guess just because a car runs does not mean the coil is good.
took it out and drove it around, runs great now.

So...good lesson.....GM ignition parts only!

BTW it was hard starting too, that also went away.

HTH