Well, we are here then...
COuld still be electrical in nature. When it is missing, you can remove one plug wire at a time - if you remove a wire from a running cylinder, teh engine will miss worse. if you remove a wire from a non-running cylinder, nothing will change. NOW you have isolated teh problem cylinder (be it mechanical or electrcial, you've found the bad one).

check that plug. replace that plug. same with wire. (IF you swap them to another cylinder, do ONE AT A TIEM (plug only, if problem moves it is the plug. not move, then try teh wire, etc).

If by chance you seem to be going in circles, it may be the coil (that is my guess at this at this time). If the problem seems to move from cylinder to cylinder (you cannot pinpoint 1 or 2 bad cylinders) then chage the coil.

You changed the plugs you said...fouled by too much gas or too little spark? Did the all look about teh same? How did they look?

You have checked all the vac lines - no leaks, cracks, splits, hooked up to the proper places, etc? Double check!

More questions if this don't fix it....let us know