Being a 94 and a carb model, I would start with cleaning out the carb float bowl. Your main jet takes over in the area that you are having the problems in and that jet is at the lowest part of the float bowl. An accumulation of rust and debris from the tank sitting in the lowest part of the float bowl could be partially clogging the high speed jet.
If you look at the bottom of the float bowl viewed from the horn side between the cylinders, there is a small brass screw there. Take a long thin screwdriver and open it up a few turns. This will purge the float bowl right below the high speed jet. The fuel will come out a drain tube in front of the rear wheel. Run a few ounces out and try the bike again at speeds to see if it solved the problem. I would open and seat the screw lightly a few times when you are done to make sure it is flushed and no debris is in the seat of the screw.
