1989 Pontiac Bonneville LE 3800 CC Motor Injector Mis-Firing #5 cylinder- Why is this happening?

We almost have the same problem. My 97 bonneville has been having issues with a misfire on cylinder #4. What I have learned so far is that a misfire on one cylinder is most likely a fouled spark plug, bad ignition wire, clogged injector or possibly bad compression such as a burned valve. There may be a slight possibility of a bad coil, but if the coil pack fires two different cylinders then it should misfire on both. I figure a person can change the coil packs around to see if the misfire moves with the coil or stays on the same cylinder.

I have looked at most of those options you both speak of.
I think it may be the computer board.
After I put the dash back together (which will take several hours) I plan on just taking it to a shop to get it fixed.
Good luck to you and many thank yous for answering!