98 Fzs6 reverting from 2/3 cyclinders to 4 constantly.

[Dead Eye]

The earlier bikes (which should be yours if your profile is right - 98/99) have three pipes coming from the tank - two small ones are breather pipes and the larger is the fuel supply to the fuel pump / filter (I forget which comes first )

If the breather pipes become kinked then it creates a vacuum in the tank which eventually will prevent fuel from being pumped out. Does the tank hiss when you open it to put fuel in? The fuel pipes could be kinked or have a build up of crap in them from years of use. Just follow the larger one from the fuel tank to the pump & filter then on to carbs