You could use bucker, tapped and split (can you get split and tapped at the same time....dont see why its not possible), and phase switching, only the tap out of which is possible with a p90, but whether you want to do that is wholly up to you. Bear in mind that the split tones of all but very powerfull buckers are weedy and gay, and wont emulate your p90 at all (parralel wiring on the bucker would probably be closer!), but the p90 doesnt have all the wiring options.