For what it may help.
My 95 LS 400 had a slight misfire - especially when accelerating.
Obviously thought of all the usual supsects, plugs, leads, ignition, timing etc.
The culprit was a leaking rocker cover gasket that was letting oil seap into two of the spark plug recesses
Eventually the top of these two plugs where covered in oil.
Every thing was dried out - gasket replaced, car now runs fine