Microsoft stopped "supporting" FS9 then even faster than they stopped "supporting" FSX... there are still a number of unresolved bugs in FS9.. one that I noticed immediately upon first getting FS9 was that the TAS calibration knob in the baron works exactly the opposite of the way it should.. I don't think they fixed that for FSX either.
At any rate - the aircraft.cfg fix to make the Baron into a turbo baron has been around a while, and the same changes that you make to the FS9 aircraft.cfg will work in FSX (don't copy the .cfg file, but make the same CHANGES to it and you're good)..
There's also a pressurized version of the Baron although I don't know that they've made any recently. There was also a "special" edition of the BE56 Baron from.. back in the 1960s I think? that had something like 350-375hp per engine and was a limited edition.. (turbocharged of course).. would like to get my hands on one of those. IIRC there was a FS2000/FS2002 model of it but I don't know that it ever got ported up to FS9/FSX.
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Scott M. Stone
WWA1712 - Cat-III - Director of Aircraft
VATSIM 1018857 - C1 Controller - KZSE
Private Pilot - ASEL + Complex + IFR (almost)