Fuel pouring out from carb outflow hose, engine running badly.

[Fazerider]

If the carb floats, valves and valve seats have already been replaced for this problem it may be that the problem is elsewhere. The fuel pump is supposed to cut off when the back pressure reaches a certain level, if the pressure switch has failed perhaps the pump can continue to force petrol into the carbs despite the resistance of the float valves.
Just a theory. I've no idea what the normal cut-off pressure is... and measuring it will require either specialist equipment or some ingenuity.
It'll be interesting to hear what your garage says.